Single-crystal silicon substrate, soi substrate, semiconductor device, display device, and manufacturing method of semiconductor device

ABSTRACT

A semiconductor device of the present invention is arranged in such a manner that a MOS non-single-crystal silicon thin-film transistor including a non-single-crystal silicon thin film made of polycrystalline silicon, a MOS single-crystal silicon thin-film transistor including a single-crystal silicon thin film, and a metal wiring are provided on an insulating substrate. With this arrangement, (i) a semiconductor device in which a non-single-crystal silicon thin film and a single-crystal silicon thin-film device are formed and high-performance systems are integrated, (ii) a method of manufacturing the semiconductor device, and (iii) a single-crystal silicon substrate for forming the single-crystal silicon thin-film device of the semiconductor device are obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.10/668,816, filed on Sep. 24, 2003, for which priority is claimed under35 U.S.C. § 120, which claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2002-280078 filed Sep. 25, 2002; Japanese PatentApplication No. 2002-299577 filed Oct. 11, 2002; and Japanese PatentApplication No. 2003-067109 filed Mar. 12, 2003 the entire contents ofwhich are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device for improvingcircuit performances of devices such as an active matrix liquid crystaldisplay device driven by TFT, in which a peripheral drive circuit and acontrol circuit are integrated on a single substrate, a manufacturingmethod of the semiconductor device, and a single-crystal siliconsubstrate used in the process of manufacturing the semiconductor device.Further, the present invention relates to an SOI (Silicon On Insulator)substrate, a display device, and a manufacturing method of asemiconductor device, and particularly relates to (i) an SOI substrateincluding a single-crystal silicon thin film which is obtained bybonding a single-crystal silicon piece, to which hydrogen ions areimplanted, with a substrate, and dividing the substrate with thesingle-crystal silicon piece at a layer to which the hydrogen ions areimplanted, (ii) a display device using the SOI substrate, and (iii) amethod of manufacturing a semiconductor device using the SOI substrate.

BACKGROUND OF THE INVENTION

There have been conventional liquid crystal display devices in which athin-film transistor (hereinafter, TFT) made of amorphous silicon(hereinafter, a-Si) or polycrystalline silicon (hereinafter, P-Si) isformed on a glass substrate, which are used for driving liquid crystaldisplay panels and organic EL panels, i.e. for performing active matrixdrive.

In particular, liquid crystal display devices in which peripheral drivesare integrated using p-Si that has high mobility and operates at a highspeed have recently been used. Even so, a silicon device with improvedperformance is required for realizing system integration of devices suchas an image processor and a timing controller which are required to haveperformance better than the above-mentioned peripheral devices.

This is because, when adopting P-Si, the mobility is decreased and an S(subthreshold) factor is increased due to localized states in a gapcaused by the incompleteness of crystallinity and the deficiency arounda grain boundary, so that the transistor does not have sufficientperformance to form a high-performance silicon device.

Thus, to form a silicon device having higher performance, researcheshave been done on such a technology that a device such as a thin-filmtransistor made of single-crystal silicon thin film is formed inadvance, and then a semiconductor device is manufactured by bonding thisthin-film transistor on an insulating substrate (e.g. WO93/15589(published on Aug. 5, 1993), J. P. Salerno, “Single Crystal SiliconAMLCDs”, Conference Record of the 1994 International Display ResearchConference (IDRC) P. 39-44 (1994), and Q.-Y. Tong & U. Gesele,“SEMICONDUCTOR WAFER BONDING: SCIENCE AND TECHNOLOGY”, John Wiley &Sons, New York (1999)).

WO93/15589 teaches that, using a semiconductor device in which asingle-crystal silicon thin-film transistor formed in advance using anadhesive is printed on a glass substrate, a display of a display panelof an active matrix liquid crystal display device is manufactured.

However, according to this conventional semiconductor device and themanufacturing method thereof, since the adhesive is used for bonding thesingle-crystal silicon thin-film transistor, which has high performance,with the glass substrate, the bonding operation is cumbersome andhinders the improvement of productivity. Further, being bonded using theadhesive, the semiconductor device has low heat resistance, and it isnot possible to form high-quality members such as an inorganicinsulating film and a TFT in the subsequent process. For this reason, onthe occasion of manufacturing an active matrix substrate, it isnecessary to form a device including a TFT array before bonding thedevice to a substrate, and this has been a great disadvantage in termsof a cost/size ratio and formation of a wiring.

Moreover, WO93/15589 only teaches that a single-crystal silicon thinfilm device is formed on a glass substrate, and according to thisarrangement, it is not possible to manufacture ahigh-performance/high-quality semiconductor device which has been soughtafter.

K. Warner, et al., 2002 IEEE International SOI Conference: October, pp.123-125 (2002) teaches that an aligning mark is detected over a siliconsubstrate by means of infrared light so that aligning is performed.However, with this arrangement, it is not possible to increaseresolution due to long wavelength of the light, and hence high-precisionaligning cannot be performed.

Further, L. P. Allen et al., 2002 IEEE International SOI Conference:October, pp. 192-193 (2002) teaches that a silicon on a BOX (BuriedOxide) is evenly etched by a halogen gas cluster ion beam (GCIB) made ofabout 1500 atoms, and a high-frequency component of surface roughness onthe surface of the silicon is removed by GCIB using oxygen.

Now, another problem which has conventionally been known will bediscussed. A thin-film transistor (TFT) technology relates tomanufacture of a transistor by forming a semiconductor film such as asilicon film on, for instance, a light-transmitting amorphous materialsuch as a glass substrate. This TFT technology has been developed inline with the diffusion of personal intelligent communicators usingliquid crystal display panels.

In the TFT technology, a polysilicon (polycrystalline) film is formedby, for instance, melting an amorphous silicon film on a substrate byapplying laser thereto. Then from this polysilicon film or amorphoussilicon film, a MOS TFT as a switching element is manufactured.

In this manner, using a device (MOS TFT) made from a silicon film,display panels such as a liquid crystal display panel and organic ELpanel are manufactured.

Then pixels of the display panel are driven in an active matrix mannerby the MOS TFT.

This arrangement has been used for devices such as a TFT liquid crystaldisplay (LCD) device, a TFT organic electro-luminescence (OLED: OrganicLight Emitting Diode) display device.

To drove the switching elements in an active matrix manner, a silicondevice with higher performance is required and system integration ofdevices such as a peripheral driver and a timing controller isnecessary.

However, it is not possible to obtain the required high performance whena conventionally-used amorphous silicon film or a polycrystal film isadopted.

This is because, in the polycrystal silicon film and the like, there arelocalized states in a gap caused by the incompleteness of crystallinityand the deficiency around a grain boundary. The existence of thelocalized states decreases the mobility. Further, due to the increase ofa subthreshold (S) factor, the performance of the transistor is causedto be insufficient so that a high-performance silicon device cannot beformed.

Moreover, when the crystallinity of the silicon film is insufficient, afixed charge tends to be formed at the interface between silicon and agate insulating film. On this account, it is difficult to control athreshold voltage of the thin-film transistor, thereby being impossibleto obtain a required threshold voltage.

In the case of the TFT liquid crystal display, a polycrystalline siliconfilm is formed from an amorphous silicon film by means of methods suchas heating using laser light. In this process, since the energy of thelaser causes a certain degree of fluctuation, the particle size of theobtained polycrystalline silicon film is not consistent. On thisaccount, the mobility and threshold voltage greatly vary.

When an amorphous silicon film formed by methods such as a plasma CVD(Chemical Vapor Deposition) is heated by laser light and thencrystallized, a temperature of a surrounding area of the film promptlyrises to be nearly a melting point of silicon. Thus, when a non-alkalihigh strain point glass is adopted as a substrate, substances such asalkaline metal are diffused into the silicon through the glass. For thisreason, the characteristics of the transistor to be obtaineddeteriorate.

To solve this problem, a device using single-crystal silicon has beendeveloped, in parallel with researches for further homogenization andimprovement of crystallinity of polycrystalline silicon.

An SOI substrate is an example of devices using such single-crystalsilicon (SOI is an abbreviation of Silicon on Insulator). SOI technologyfor the SOI substrate mainly relates to formation of a single-crystalsemiconductor thin film on an amorphous substrate. This term, SOItechnology, is not frequently used in respect of formation of apolycrystalline silicon film. SOI technology has been actively developedsince 1980s.

As an example of the SOI substrate, there is a SIMOX (Separation byImplanted Oxygen) substrate which has been commercially available. ThisSIMOX substrate is formed by implanting oxygen into a silicon wafer. Inthis process, since oxygen, which is a relatively heavy element, isimplanted to a predetermined depth, a crystalline structure of thesilicon wafer is seriously damaged due to an accelerating voltageinvolved in the implantation. Thus, the SIMOX substrate has such aproblem that the characteristics of single-crystal on the substrate arenot sufficient. Further, the insulation performance is inadequate due tonon-stoichiometry of a silicon dioxide film layer, and since a largeamount of oxygen is required for the implantation, the costs for the ionimplantation is high.

In response to this, Japanese Laid-Open Patent Application No.5-211128/1993 (Tokukaihei 5-211128; published on Aug. 20, 1993)discloses a method of manufacturing a thin semiconductor film, which isarranged such that a single-crystal silicon piece is bonded on a siliconbase substrate covered with an oxidized silicon film, and the resultantsubstrate with the silicon piece is manufactured to be a thin film.

According to this technology, a single-crystal silicon thin film can beformed on a single-crystal silicon base substrate on which an oxidizedfilm has been formed in advance.

Japanese Laid-Open Patent Application No. 2000-30996 (Tokukai2000-30996; published on Jan. 28, 2000) discloses a standard deviationof thickness of an oxidized film on a silicon wafer, regarding an SOIwafer and a manufacturing method thereof.

Also, Japanese Laid-Open Patent Application No. 6-268183/1994(Tokukaihei 6-268183; published on Sep. 22, 1994) discloses a method ofmanufacturing a semiconductor device, in which method athinly-manufactured substrate on which a semiconductor device has beenformed is transferred to another supporting substrate.

In this method, after a semiconductor element is formed on one side of asemiconductor layer, the semiconductor layer manufactured as a thinlayer is bonded with a supporting substrate, by means of cold anodeconnection.

However, in this arrangement, micro-roughness of the oxidized siliconfilm on the substrate weakens the adhesive power so that film strippingoccurs.

That is to say, according to Japanese Laid-Open Patent Application No.5-211128/1993, the thickness of the oxidized film is significantlyirregular when the film on the silicon base substrate is thickly formed.Thus, the irregularity of the surface becomes noticeable and theadhesiveness of the bonding and the characteristics of the SOI substratedeteriorate.

Note that, although Japanese Laid-Open Patent Application No. 2000-30996includes the description regarding uniformity of the thickness of thesingle-crystal silicon thin film on occasions when the standarddeviation of the thickness is large. However, the document does notmention the problems such as the formation of voids on the occasion ofbonding and the stripping of the silicon film on the occasion ofseparation and stripping.

Further, Japanese Laid-Open Patent Application No. 6-268183/1994 doesnot describe the micro-roughness and flatness of the thinnedsemiconductor layer and the supporting substrate.

In this manner, the micro-roughness of the oxidized silicon film bywhich a light-transmitting substrate is covered weakens the adhesivepower. On this account, separation and stripping occur so that the yielddecreases due to reasons such as the film stripping after forming asilicon film on a substrate.

SUMMARY OF THE INVENTION

To solve the above-described problem, the objective of the presentinvention is to provide (i) a semiconductor device in which asingle-crystal silicon thin-film device can be easily formed on aninsulating substrate without using an adhesive, a non-single-crystalsilicon thin film and a single-crystal silicon thin-film device areformed, and high-performance systems are integrated, (ii) a method ofmanufacturing the semiconductor device, and (iii) a single-crystalsilicon substrate for forming the single-crystal silicon thin film ofthe semiconductor device. Another objective of the present invention isto provide a method of manufacturing an SOI substrate in which anadhesive strength is enhanced, a display device, and a semiconductordevice.

To achieve the foregoing objectives, the single-crystal siliconsubstrate of the present invention is characterized in that an oxidizedfilm, a gate pattern, and an impurity ion implanted interface on asurface of the single-crystal silicon substrate, and the surface isplanarized after forming the oxidized film, the gate pattern, and theimpurity ion implanted interface, and a dense position of implantedhydrogen ions, to which a predetermined concentration of hydrogen ionsis implanted for a predetermined depth.

According to this arrangement, the side of the single-crystal siliconsubstrate, where the oxidized film is formed, is bonded with a membersuch as the insulating substrate, and owing to the heat treatment, thesubstrates are bonded with siloxane bond so that the substrates becometightly bonded, and also, since the cleavage stripping at the denseposition is conducted by heating, it is possible to obtain a MOSsingle-crystal silicon thin-film transistor with ease, even if anadhesive is not used.

That is to say, the single-crystal silicon substrate of the presentinvention is arranged so that, on the surface thereof, the oxidizedfilm, gate pattern, and impurity ion implanted interface are formed asparts of the MOS single-crystal silicon thin-film transistor, and thedense position of implanted hydrogen ions is provided at a predetermineddepth from the surface.

According to this arrangement, a single-crystal silicon substrate (inwhich the impurity doping for the gate electrode and for the source anddrain, and the impurity doping for the base, collector and emitter arecarried out, a predetermined concentration of hydrogen ions is implantedfor a predetermined depth, and the surface is planarized and caused tobe hydrophilic) is bonded on an insulating substrate, and then heatingis carried out so that a temperature is increased to be not less thanthe temperature of hydrogen dissociation from silicon. Thus, it ispossible to increase the adhesive strength with respect to theinsulating substrate, and since the cleavage stripping at the denseposition is carried out, it is possible to easily form a MOSsingle-crystal silicon thin-film transistor, without using an adhesive.

On this account, for instance, on an insulating substrate on which anon-single-crystal (e.g. polycrystalline) silicon thin-film transistoris formed, the single-crystal silicon substrate of the present inventionis bonded so that a MOS single-crystal silicon thin-film transistor isformed. With this arrangement, it is possible to easily obtain asemiconductor device in which a transistor made of non-single-crystalsilicon and a transistor made of single-crystal silicon are formed ondifferent areas of a single substrate.

To achieve the above-mentioned objectives, the SOI substrate of thepresent invention, in which a single-crystal thin film is provided on aninsulating substrate, is characterized by comprising: a bonded interfaceat which an insulating film formed on the insulating substrate is bondedwith a covering film (note that, in the present invention, the term“covering film” indicates either a covering film or a thermally oxidizedfilm) with which the single-crystal silicon substrate is covered, thesingle-crystal silicon substrate being separated at the dense positionso that the single-crystal silicon thin film is formed, the insulatingsubstrate being a light-transmitting substrate, and the single-crystalsilicon substrate being separated by means of heat treatment.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture transistors which can meet strict demands for thevariation and performance.

Also, since the insulating substrate is a light-transmitting substrate,the SOI substrate can be adopted as an active matrix substrate of adisplay device.

Also, since hydrogen ions which are much lighter than oxygen ions areimplanted, the implantation does not significantly change thecrystalline on the entire surface of the single-crystal siliconsubstrate, and hence such a problem of the degradation of thecrystalline of the silicon due to the implantation of hydrogen ions canbe resolved.

Also, by the heat treatment, the condition of the crystalline of thesingle-crystal silicon thin film is recovered to be the level before theimplantation of the hydrogen ions. The heat treatment is carried out ata temperature about, for instance, 600° C. This treatment does notdeteriorate the bonding characteristics at the bonded interface.

To achieve the above-mentioned objectives, the SOI substrate of thepresent invention, in which a single-crystal silicon thin film isprovided on an insulating substrate, is characterized by comprising: abonded interface at which an insulating film formed on the insulatingsubstrate is bonded with a covering film with which a single-crystalsilicon substrate is covered, the single-crystal silicon thin film beingformed by separating the single-crystal silicon substrate at a denseposition of implanted hydrogen ions by means of heat treatment, and atthe bonded interface, the insulating film is arranged to satisfy that atan θ is not more than 0.06, where θ is the angle between (i) a maximumslope curve of micro-roughness, the micro-roughness being measured in a1-5 μm square and not more than 5 nm in height, and (ii) an averagesurface plane.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture transistors which can meet strict demands for thevariation and performance.

Note that, the tangent in the present case is an absolute value of thetangent. For this reason, in the arrangement above, the absolute valueof the tangent is not less than 0 and not more than 0.06. The foregoinginsulating film has micro-roughness on its surface, and the tangent ofthe maximum slope of micro-roughness on the surface of the insulatingfilm to the surface plane of the insulating substrate, measured in a 1-5μm square, is not more than 0.06, More specifically, for instance, thetangent of the maximum slope of micro-roughness on the surface of theinsulating film to the surface plane of the insulating substrate,measured in a 1-5 μm square, is not more than 0.06, the micro-roughnessbeing not more than 5 nm in height.

By restraining the micro-roughness to be small as above, it is possibleto enhance the adhesive strength between the insulating film and thecovering film with which the single-crystal silicon substrate iscovered.

Further, the tangent is more preferably not more than 0.04. Thisarrangement makes it possible to further enhance the adhesive strengthbetween the insulating film and the covering film with which thesingle-crystal silicon substrate is covered.

Thus, it is possible to solve such a problem that the bondingcharacteristics between a light-transmitting substrate and asingle-crystal silicon substrate are degraded due to the micro-roughnesson the surface of the light-transmitting substrate.

Note that, in the SOI substrate, the condition of the surface of theinsulating film used for bonding the insulating substrate with thesingle-crystal silicon substrate can be evaluated by performing an AFMmethod with respect to, for instance, the micro-roughness of the surfacewhich is caused by the separation of the insulating substrate from thesingle-crystal silicon substrate.

To achieve the above-mentioned objectives, the semiconductor device ofthe present embodiment is characterized in that a non-single-crystalsilicon device and a single-crystal silicon thin-film device are formedin different areas of the insulating substrate.

The non-single-crystal silicon thin-film device is made by anon-single-crystal silicon thin film provided on the insulatingsubstrate. The single-crystal silicon thin-film device is provided onthe single-crystal silicon substrate, and then this single-crystalsilicon substrate is separated so that a single-crystal silicon thinfilm is provided on the insulating film, and consequently thesingle-crystal silicon thin-film device is provided on the insulatingfilm. Alternatively, the single-crystal silicon thin-film device may bemade from a single-crystal silicon thin film provided on the insulatingsubstrate.

According to the above, for instance, a single-crystal silicon thin-filmdevice such as a single-crystal silicon thin-film transistor is adoptedto devices which have to be highly functional, such as a timingcontroller, while a non-single-crystal silicon thin-film device such asa non-single-crystal silicon thin-film transistor is adopted to otherdevices. With this arrangement, it is possible to obtain a semiconductordevice in which high-performance and highly-functional circuit systemsare integrated.

That is to say, by adopting a single-crystal silicon thin-film device,devices such as a fast and low-power-consumption logic circuit andtiming generator and a fast DAC (current buffer) from which variationhas to be eliminated can be formed. Meanwhile, although the performanceand characteristics of a non-single-crystal silicon (e.g.polycrystalline silicon) thin-film device are inferior to theperformance and characteristics of the single-crystal silicon thin-filmdevice, it is possible to form a large and cheap semiconductor device byadopting the non-single-crystal silicon thin-film device.

Thus, according to the present invention, it is possible to form asemiconductor device having the advantages of the both silicon thin-filmdevices, on a single substrate.

On this account, high-performance and highly-functional circuit systemswhich can be realized only by adopting single-crystal silicon can beintegrated on a single substrate. For instance, a semiconductor devicefor a display device in which high-performance systems are integrated,such as a liquid crystal panel and an organic EL panel, can bemanufactured with significantly lower costs, compared to a case when alldevices are made by single-crystal silicon.

The shape of the single-crystal silicon substrate by which thesingle-crystal silicon thin film of the semiconductor device of thepresent invention is formed has to be a disk which is sized 6, 8, or 12inch in diameter. Note that, the disk which is sized 6, 8, or 12 inch indiameter is a typical wafer for manufacturing LSI. However, since thenon-single-crystal silicon thin-film device and the single-crystalsilicon thin-film device coexist on the insulating substrate of thesemiconductor device of the present invention, it is possible tomanufacture, for instance, a large semiconductor device which can beadopted to a large liquid crystal display panel and a large organic ELpanel.

To achieve the foregoing objectives, the display device of the presentinvention is characterized by comprising the above-mentioned SOIsubstrate in which a semiconductor device structure is formed. This SOIsubstrate is a semiconductor device in which a semiconductor devicestructure is formed.

Further, to achieve the foregoing objectives, the display device of thepresent invention includes any one of the foregoing semiconductordevices, and the semiconductor device is adopted as an active matrixsubstrate for a display panel.

In the SOI substrate, since an insulating substrate is alight-transmitting substrate, forming a semiconductor device structureon the insulating substrate makes it possible to suitably use thesemiconductor device as an active matrix substrate for a display panel.

Also, since a high-performance transistor with no variation can beobtained by adopting the SOI substrate, it is possible to obtain ahigh-performance display device by adopting this transistor.

In this manner, by adopting the single-crystal silicon, thecharacteristics of the transistor can be caused to be uniform,stabilized, and high-performance, and hence it is possible tomanufacture, for instance, a high-performance MOS field effecttransistor device. On this account, using this transistor device, it ispossible to manufacture a high-performance TFT-LCD display device,TFT-OLEDL display device, and IC.

Note that, the semiconductor device structure is, for instance, astructure as a switching element for displaying. Also, it is possible tomanufacture an image processor by forming a semiconductor devicestructure on an SOI substrate.

To achieve the foregoing objective, the method of manufacturing thesemiconductor device of the present invention, in which a single-crystalsilicon thin-film device manufactured from a single-crystal silicon thinfilm and a non-single-crystal silicon thin film are formed on aninsulating substrate, is characterized in that, after a circuitincluding the single-crystal silicon thin-film device is formed on theinsulating substrate, the non-single-crystal silicon thin film isformed.

According to this method, the single-crystal silicon thin-film device isformed on an insulating substrate which is the most flattened, and thenthe non-single-crystal silicon thin film is formed. Thus, it is possibleto manufacture semiconductor devices in which defects due to the bondingerror are rarely found, with good production yields.

To achieve the foregoing objectives, the method of manufacturing thesemiconductor device of the present invention, in which a single-crystalsilicon thin-film device manufactured from a single-crystal silicon thinfilm and a non-single-crystal silicon thin film are formed on aninsulating substrate, is characterized in that, after thenon-single-crystal silicon thin film is formed on the insulatingsubstrate, the single-crystal silicon thin-film device is formed.

According to this method, contrary to the arrangement that thenon-single-crystal silicon thin-film device is formed after forming thesingle-crystal silicon thin film, the non-single-crystal silicon thinfilm is formed before the formation of the single-crystal siliconthin-film device and hence it is possible to prevent the contaminationand damage of the single-crystal silicon thin film.

To achieve the foregoing objectives, the method of manufacturing thesemiconductor device of the present invention, comprising the step of:(a) bonding an insulating film formed on an insulating substrate with acovering film with which a single-crystal silicon substrate is covered,is characterized by further comprising the step of: (b) before the step(a), regulating a tangent of a maximum slope of micro-roughness on asurface of the insulating film to a surface plane of the insulatingsubstrate, measured in a 1-5 μm square, is not more than 0.06, themicro-roughness being not more than 5 nm in height.

The SOI substrate is manufactured in such a manner that, after thebonding step, the single-crystal silicon substrate is separated andstripped at the dense position and thus the single-crystal silicon thinfilm is formed. That is to say, the above-described manufacturing methodis also a method of manufacturing an SOI substrate. According to themanufacturing method, a semiconductor device is manufactured either byforming a semiconductor device structure on a single-crystal siliconthin film on the SOI substrate, or manufacturing a single-crystalsilicon thin film from a single-crystal silicon substrate in which asemiconductor device structure is formed.

According to the manufacturing method, after the micro-roughness on thesurface of the insulating film is arranged so that the tangent of themaximum slope of the micro-roughness to the surface of the insulatingsubstrate is not more than 0.06, the insulating film is bonded with thecovering film with which the single-crystal silicon substrate iscovered. With this arrangement, the bonding characteristics are good sothat the adhesive strength is improved. Thus, the peeling of the filmdoes not occur when the single-crystal silicon substrate is separatedand stripped in order to form the single-crystal silicon thin film,after the bonding step.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a cross section indicating a manufacturing process of oneembodiment of a semiconductor device in accordance with the presentinvention.

FIG. 1( b) is a cross section indicating another manufacturing processof the semiconductor device of FIG. 1( a).

FIG. 1( c) is a cross section indicating a further manufacturing processof the semiconductor device of FIG. 1( a).

FIG. 1( d) is a cross section indicating yet another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 1( e) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 1( f) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 1( g) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 1( h) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 1( i) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 1( a).

FIG. 2( a) is a cross section indicating a manufacturing process ofanother embodiment of a semiconductor device in accordance with thepresent invention.

FIG. 2( b) is a cross section indicating another manufacturing processof the semiconductor device of FIG. 2( a).

FIG. 2( c) is a cross section indicating a further manufacturing processof the semiconductor device of FIG. 2( a).

FIG. 2( d) is a cross section indicating yet another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 2( e) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 2( f) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 2( g) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 2( h) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 2( i) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 2( a).

FIG. 3( a) is a cross section indicating a manufacturing process of afurther embodiment of a semiconductor device in accordance with thepresent invention.

FIG. 3( b) is a cross section indicating another manufacturing processof the semiconductor device of FIG. 3( a).

FIG. 3( c) is a cross section indicating a further manufacturing processof the semiconductor device of FIG. 3( a).

FIG. 3( d) is a cross section indicating yet another manufacturingprocess of the semiconductor device of FIG. 3( a).

FIG. 3( e) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 3( a).

FIG. 3( f) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 3( a).

FIG. 4 is a schematic cross section illustrating a bipolarsingle-crystal silicon thin-film transistor of FIG. 3.

FIG. 5( a) is a cross section indicating a manufacturing process of yetanother embodiment of a semiconductor device in accordance with thepresent invention.

FIG. 5( b) is a cross section indicating another manufacturing processof the semiconductor device of FIG. 5( a).

FIG. 5( c) is a cross section indicating a further manufacturing processof the semiconductor device of FIG. 5( a).

FIG. 5( d) is a cross section indicating yet another manufacturingprocess of the semiconductor device of FIG. 5( a).

FIG. 5( e) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 5( a).

FIG. 5( f) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 5( a).

FIG. 6( a) is a cross section indicating a manufacturing process ofstill another embodiment of a semiconductor device in accordance withthe present invention.

FIG. 6( b) is a cross section indicating another manufacturing processof the semiconductor device of FIG. 6( a).

FIG. 6( c) is a cross section indicating a further manufacturing processof the semiconductor device of FIG. 6( a).

FIG. 6( d) is a cross section indicating yet another manufacturingprocess of the semiconductor device of FIG. 6( a).

FIG. 6( e) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 6( a).

FIG. 6( f) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 6( a).

FIG. 6( g) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 6( a).

FIG. 6( h) is a cross section indicating still another manufacturingprocess of the semiconductor device of FIG. 6( a).

FIG. 7 is a plan view, illustrating an active matrix substratemanufactured using the semiconductor device of the present invention.

FIG. 8 is a graph, showing the difference of linear expansion ofsingle-crystal silicon and a glass substrate, at temperatures between aroom temperature and 600° C.

FIG. 9 is a conceptual diagram regarding alignment of a single-crystalsilicon with a glass substrate at a room temperature, in a method ofmanufacturing the semiconductor device of the present invention.

FIG. 10 is a cross section illustrating an embodiment of an SOIsubstrate of the present invention.

FIG. 11( a) is a cross section of an insulating substrate included inthe above-mentioned SOI substrate.

FIG. 11( b) is a cross section illustrating the state of depositing aninsulating film on the above-mentioned insulating substrate.

FIG. 11( c) is a cross section of a single-crystal silicon substrate.

FIG. 11( d) is a cross section illustrating the state of covering thesingle-crystal silicon substrate with a covering film.

FIG. 11( e) is a cross section illustrating the state of implantinghydrogen ions into the single-crystal silicon substrate of FIG. 11( d).

FIG. 11( f) is a cross section illustrating the state of bonding theinsulating substrate of FIG. 11( b) to the single-crystal siliconsubstrate of FIG. 11( e).

FIG. 11( g) is a cross section illustrating the state of manufacturingthe above-mentioned SOI substrate by separating and stripping thesingle-crystal silicon substrate.

FIG. 12 is a cross section illustrating micro-roughness on the surfaceof the above-mentioned insulating film deposited on the above-mentionedinsulating substrate.

FIG. 13 is a cross section, indicating water-wettability of the surfaceof the above-mentioned insulating substrate deposited on theabove-mentioned insulating film.

FIG. 14( a) is a cross section of an insulating substrate included inthe above-mentioned SOI substrate.

FIG. 14( b) is a cross section illustrating the state of depositing aninsulating film on the insulating substrate.

FIG. 14( c) is a cross section illustrating the state of depositing anamorphous silicon film on the insulating substrate of FIG. 14( b).

FIG. 14( d) is a cross section illustrating the melting of the amorphoussilicon film caused by applying excimer laser.

FIG. 14( e) is a cross section illustrating the state that a polysiliconfilm is formed.

FIG. 14( f) is a cross section illustrating the state that an area onwhich the single-crystal silicon substrate is mounted is formed by meansof photolithography.

FIG. 14( g) is a cross section illustrating the state that thesingle-crystal silicon substrate is mounted.

FIG. 14( h) is a cross section illustrating the manufacture of the SOIsubstrate by separating and stripping the single-crystal siliconsubstrate.

FIG. 15 is a cross section illustrating an example of a thin-filmtransistor which is manufactured using the above-mentioned SOIsubstrate.

FIG. 16 is a cross section illustrating the state of micro-roughness ofthe surface of an oxidized silicon film deposited on a substrate, in thecase of a conventional arrangement.

FIG. 17 is a schematic cross section, illustrating an appraisal methodof bonding power.

FIG. 18 is a block diagram, illustrating an example of a display deviceadopting the semiconductor device of the present invention.

FIG. 19 is a cross section indicating still another manufacturingprocess of the semiconductor device of the present invention.

FIG. 20 is a cross section indicating a part of still anothermanufacturing process of the semiconductor device of the presentinvention.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

The following will describe a single-crystal silicon substrate, asemiconductor device, and a manufacturing method thereof in accordancewith an embodiment of the present invention. FIGS. 1( a)-1(i) are crosssections illustrating a manufacturing process of a semiconductor deviceof the present embodiment. The semiconductor device of the presentembodiment is a high-performance and highly-functional semiconductordevice in which a MOS non-single-crystal silicon thin-film transistorand a MOS single-crystal silicon thin-film transistor are formed ondifferent areas of the surface of an insulating substrate, thesemiconductor device being formed on a TFT active matrix substrate.

The MOS thin-film transistor includes an active semiconductor layer,gate electrodes, a gate insulating film, and high-concentration impuritydoped sections (source and drain electrodes) formed on the both sides ofthe gate. The MOS thin-film transistor is a typical transistor in whichthe gate electrodes modulate the carrier density of a semiconductorlayer below the gate so that the current running between the source anddrain is controlled.

When the MOS transistor adopts a CMOS (Complementary MOS) structure,since the power consumption is low and the output can swing up to thepower-supply voltage, the MOS transistor is suitable for the logic oflow-power-consumption type.

As FIG. 1( i) illustrates, a semiconductor device 20 of the presentembodiment is arranged in such a manner that, on an insulating substrate2, a SiO₂ (oxidized Si) film (insulating film) 3, a MOSnon-single-crystal silicon thin-film transistor 1 a including anon-single-crystal silicon thin film 5′ made of polycrystalline silicon,a MOS single-crystal silicon thin-film transistor (single-crystalsilicon thin-film device) 16 a including a single-crystal silicon thinfilm 14 a, and a metal wiring 22 are provided.

As the insulating substrate 2, code 1737 (alkaline-earthalumino-borosilicate glass) of Corning®, which is a high strain pointglass is adopted.

The SiO₂ film 3, which is about 50 nm thick, is formed so as to coverthe entire surface of the insulating substrate 2.

In the MOS non-single-crystal silicon thin-film transistor 1 a includingthe non-single-crystal silicon thin film 5′, the non-single-crystalsilicon thin film 5′, a SiO₂ film 7 as a gate insulating film, and gateelectrodes 6 are formed on a SiO₂ film 4 which functions as aninterlayer insulating film.

Although the gate electrodes 6 are made of polysilicon silicon and Wsilicide, the gate electrodes 6 may be made of substances such aspolycrystalline Si, other types of silicide, and polycide.

The MOS single-crystal silicon thin-film transistor 16 a including thesingle-crystal silicon thin film 14 a is provided with a planarizinglayer including gate electrodes 12, a SiO₂ film 13 as a gate insulatingfilm, and the single-crystal silicon thin film 14 a.

Although the gate electrodes 12 are made of a heavily-doped polysiliconsilicon film and W silicide, the gate electrodes 12 may be sorely madeof polycrystalline silicon or made of other types of high melting pointmetal or silicide, and the materials are selected in accordance with arequired level of electrical resistance and heat resistance.

The single-crystal silicon thin-film transistor 16 a is formed on thesingle-crystal silicon substrate before being bonded to the insulatingsubstrate 2. Areas to be formed as the gate electrodes 12 are bonded tothe insulating substrate 2, and on this occasion, the areas include agate insulating film 13 and the single-crystal silicon thin film 14 a.Thus, when the formation of the gate electrodes and the implantation ofimpurity ions to the source and drain are performed on thesingle-crystal silicon substrate 10 a, micro-fabrication is easilyconducted, compared to a case when the formation of the thin-filmtransistor is carried out after the formation of the single-crystalsilicon thin film on the insulating substrate 2.

As described above, the semiconductor device 20 of the presentembodiment is a high-performance and highly-functional semiconductordevice in which a plurality of circuits having different characteristicsare integrated, which is realized by causing the MOS non-single-crystalsilicon thin-film transistor 1 a to be coexistence with the MOSsingle-crystal silicon thin-film transistor 16 a on the singleinsulating substrate 2. Moreover, the present arrangement makes itpossible to obtain a high-performance and highly-functionalsemiconductor device with low costs, compared to a case of forming atransistor which is entirely made of a single-crystal silicon thin filmon a single insulating substrate 2.

Note that, the distance between an area of the non-single-crystalsilicon thin film 5′ an area of the single-crystal silicon thin film 14a is at least 0.3 μm, preferably not less than 0.5 μm. With thisarrangement, it is possible to prevent metal elements such as Ni, Pt,Sn, and Pd from being diffused to the crystal silicon thin film 14 a,thereby stabilizing the characteristics of the single-crystal siliconthin-film transistor 16 a.

Further, in the semiconductor device 20 of the present embodiment, aSiO₂ film 4 is formed as an interlayer insulating film between thenon-single-crystal Si thin-film transistor 1 a and the single-crystalsilicon thin-film transistor 16 a. With this arrangement, it is possibleto prevent the contamination of the single-crystal silicon thin film 14a.

For instance, in the case of an active matrix substrate of the liquidcrystal display device including the semiconductor device 20 of thepresent invention, SiN_(x) (silicon nitride), resin planarized film, avia hole, and a transparent electrode are provided for the sake ofliquid crystal displaying. Also, in the area of the non-single-crystalsilicon thin film 5′, TFTs for the driver section and display sectionare formed, while in the area of the single-crystal silicon thin film 14a which can accommodate high-performance devices, a timing controller isformed. The driver section may be made of single-crystal Si, providedthat it is worthwhile in terms of costs and performance.

In this manner, the functions and purposes of the respective thin-filmtransistors are determined in accordance with the characteristics of thesingle-crystal silicon thin film 14 a and non-single crystal siliconthin film 5′ by which the transistors are formed, and this makes itpossible to obtain high-performance and highly-functional thin-filmtransistors.

Note that, while the mobility of an N-channel TFT formed in the area ofa conventional non-single-crystal silicon thin film 5′ is about 100cm²/V·sec, in the active matrix substrate for liquid crystal displayingin which the semiconductor device of the present embodiment is formed,the mobility of the N-channel TFT formed in the area of thesingle-crystal silicon thin film 14 a is about 550 cm²/V·sec. Thisproves that the semiconductor device 20 of the present embodiment makesit possible to obtain a TFT which can operate faster than conventionalTFTs.

Further, in this active matrix substrate for liquid crystal displaying,while devices formed in the area of the non-single-crystal silicon thinfilm 5′, such as the driver, require a signal and power-supply voltageof 7-8V, the timing controller which is formed in the area of thesingle-crystal silicon thin film 14 a stably operates at 2.7V.

In the semiconductor device 20, ICs including a pixel array are formedin areas suitable for required arrangement and characteristics, i.e.formed in either appropriate one of the area of the non-single-crystalsilicon thin film 5′ and the area of the single-crystal silicon thinfilm 14 a. Further, the ICs in the respective areas can be formed so asto have different characteristics such as working speeds and workingpower-supply voltages. For instance, it is possible to arrange thesemiconductor device 20 in such a manner that, at least one of the gatelength, thickness of the gate insulating film, power-supply voltage, andlogic level is different between the areas.

With this arrangement, it is possible to form devices having differentcharacteristics in the respective areas, thereby providing asemiconductor device having greater variety of functions.

Further, in the semiconductor device 20, since the ICs are formed in thearea of the non-single-crystal silicon thin film 5′ and the area of thesingle-crystal silicon thin film 14 a, the ICs formed in the respectiveareas can be formed in accordance with respective manufacturing rulespeculiar to the areas. This is because, for instance, when the channellength is short, there is no grain boundary in the area of thesingle-crystal silicon thin film so that the variation of the TFTcharacteristics rarely increases, while, in the area of the polysiliconsilicon thin film, the variation rapidly increases due to the existenceof the grain boundary so that the manufacturing rules have to bemodified so as to be different in the respective areas. Thus, it ispossible to form the respective ICs in suitable areas, in accordancewith the manufacturing rules.

Further, in the semiconductor device 20 of the present embodiment, themetal pattern of the MOS single-crystal silicon thin-film transistor 16a can be formed in accordance with a wiring rule which is relaxed incomparison with the wiring rule of the gate pattern.

With this arrangement, at least a part of the metal wiring of thesemiconductor device, in which the MOS single-crystal silicon thin-filmtransistor 16 a is formed, can be processed simultaneously with themetal wiring on a large substrate, and this makes it possible to reducecosts and improve processing power. Further, since the connection to anexternal wiring, other circuit blocks, and the TFT array becomes easy,the alignment failure is reduced so that the rejection rate is improved.

Note that, the size of the single-crystal silicon thin film 14 a formedon the semiconductor device 20 is determined in accordance with the sizeof an wafer of an LSI manufacturing device. For providing devices suchas a fast and low-power-consumption logic generator and timing generatorand a fast DAC (current buffer) and processor which should below-variation, which are required to be formed by the single-crystalsilicon thin film 14 a, a conventional LSI manufacturing device has asufficient size.

The following will describe a method of manufacturing the semiconductordevice 20, with reference to FIGS. 1( a)-1(i).

First, applying a gas in which TEOS is mixed with O₂ to the entiresurface of the insulating substrate 2, a SiO₂ film 3 which is about 5 nmthick is deposited by plasma CVD.

In the method of manufacturing the semiconductor device 20 of thepresent embodiment, the single-crystal silicon substrate 10 a, on whicha part to be the single-crystal silicon thin-film transistor 16 a whenbeing thinned is formed in advance, is formed on this occasion, and thissingle-crystal silicon substrate 10 a is formed on the insulatingsubstrate 2.

More specifically, after a part of the CMOS process is carried out inadvance in a typical IC manufacturing line, i.e. after the gateelectrodes 12, gate insulating film 13, protective insulating film, andplanarized film (BPSG) are formed and implantation of impurity ions(BF²⁺, P⁺) to the source and drain is carried out, the planarization isperformed by CMP (Chemical-Mechanical Polishing). Subsequently, a SiO₂film which is 10 nm thick is formed, and the single-crystal siliconsubstrate 10 a having a dense position 15 of implanted hydrogen ions, towhich hydrogen ions, a doze amount of 5×10¹⁶/cm², are implanted with apredetermined energy is formed. Then these members are reshaped so as tohave predetermined sizes corresponding to the formation area on theinsulating substrate 2. Note that, at the dense position 15 of implantedhydrogen ions, the concentration of hydrogen ions is at the maximum.

Subsequently, as FIG. 1( b) shows, the transparent insulating substrate2 and the single-crystal silicon substrate having been reshaped arewashed using SC-1 and activated, then a side of the single-crystalsilicon substrate 10 a, the side close being to the dense position 15,is aligned with a predetermined position, and the side and thepredetermined position are caused to be intimately in contact with eachother so as to be bonded with each other, at room temperatures.

The alignment is, as FIG. 9 illustrates, carried out in such a mannerthat, an aligning mark 94 on the single-crystal silicon and an aligningmark 93 of the transparent substrate 2 which is code 1737 of Corning® inthe present embodiment are detected through the transparent substrate 2,under visible light. In the example of FIG. 9, the aligning mark 94 onthe single-crystal silicon on an aligning stage 91 is detected using analigning CCD camera 90 attached to a microscope in an epi-illuminationmanner, and the result of the detection is eventually converted toelectric signals and processed.

In a conventional method that aligning is carried out by irradiatinginfrared light over a silicon substrate, since devices such as ICs arenot transparent to visible light or UV light, an alignment mark isdetected over an silicon wafer having a non-mirror and light-scatteringsurface in order to prevent sticking, and hence the alignment cannot beprecisely carried out.

To solve this problem, the semiconductor device of the presentembodiment is arranged in such a manner that, for instance, the aligningmarks 93 and 94 are detected through a glass which is transparent tovisible light or UV light having wavelengths shorter than infrared lightand has a surface which rarely scatter light. With this arrangement, thealignment can be performed more precisely than the conventionalarrangement.

Moreover, in the present embodiment, the margin of the alignment carriedout using the aligning mark 94 on the single-crystal silicon is smallerthan the margin of the alignment of the pattern of the transparentsubstrate on the whole, the display area, or the device on the whole,and hence the margin of the alignment is carried out more precisely.

Thus, when, in the subsequent step, the metal wiring 22 which iscommonly shared by the area of the non-single-crystal silicon (area ofthe non-single-crystal silicon thin film 5′), it is possible toperforate a contact hole 21 using a more precise exposure system, andusing the metal wiring 22, it is possible to easily and effectivelyconnect the area of the single-crystal silicon having a highly precisepattern with the area of the single-crystal silicon having a moderatelyprecise pattern, with a high yield ratio.

The single-crystal silicon is bonded to the glass transparent substrate2 by Van der Waals force. Subsequently, the reaction ofSi—OH+—Si—OH→Si—O—Si+H₂O is caused to occur at temperatures of 400-600°C., in this case about 550° C., so that the atoms are caused to beclosely bonded. Then, as FIG. 1( c) illustrates, the temperature of thedense position 15 is increased to be not less than the temperature ofhydrogen dissociation from the single-crystal silicon, and this makes itpossible to carry out cleavage stripping at the dense position 15 as aborder.

Here, the single-crystal silicon thin-film transistor 16 a is bonded tothe insulating substrate 2 via the inorganic insulating film 3. Thus,compared to the case of the bonding using a conventional adhesive, it ispossible to prevent the contamination of the single-crystal silicon thinfilm 14 a with more certainty.

Subsequently, an unnecessary part of the single-crystal silicon thinfilm 14 a, the part being left over on the insulating substrate 2 afterthe stripping, is removed by etching, and the single-crystal silicon ismanufactured so as to be island-shaped. Then a damaged layer on thesurface is removed by isotropic plasma etching or wet etching. In thepresent case, the layer is lightly etched for about 10 nm by wet etchingusing buffer hydrofluoric acid. On this account, as FIG. 1( i)illustrates, a part of the MOS TFT is formed on the single-crystalsilicon thin film 14 a, which is about 50 nm thick, on the insulatingsubstrate 2.

Then as FIG. 1( d) shows, on the entire surface of the insulatingsubstrate 2, a second SiO₂ film 4 which is about 200 nm thick isdeposited by plasma CVD using a gas in which SiH₄ and N₂O are mixed.Then on the entire surface, an amorphous silicon film 5 which is 50 nmthick is deposited by plasma CVD using a SiH₄ gas.

By irradiating the amorphous silicon film 5 with excimer laser forheating and crystallization, a polycrystalline silicon layer isdeveloped so that the non-single-crystal silicon thin film 5′ is formedand the adhesive strength between the single-crystal silicon thin film14 a and the insulating film 3 is increased.

Next, as FIG. 1( f) illustrates, an unnecessary part of thepolycrystalline silicon film 5′ is removed in order to cause a part,which becomes an active area of the device, to be left, and consequentlyan island-shaped pattern is obtained.

Then using a gas in which TEOS is mixed with oxygen, a SiO₂ film whichis about 350 nm thick is deposited by plasma CVD, and this SiO₂ film isetched for about 400 nm by RIE. Subsequently, as a gate insulating filmof the non-single-crystal silicon thin-film transistor 1 a, a SiO₂ film7 which is about 60 nm thick is formed by plasma CVD using a gas inwhich SiH₄ is mixed with N₂O. On this occasion, side walls are formed atthe respective end portions of the single-crystal silicon thin film 14 aand the non-single-crystal silicon thin film 5′.

Next, as FIG. 1( g) illustrates, as an interlayer planarized insulatingfilm (protective interlayer insulating film), a SiO₂ film 8 which isabout 350 nm thick is deposited by P-CVD using a gas in which TEOS ismixed with O₂ (oxygen).

Then the contact hole 21 is opened as FIG. 1( h) shows, and the metal(AlSi) wiring 22 is formed on the contact hole 21 as FIG. 1( i)illustrates.

As described above, in the method of manufacturing the semiconductordevice of the present embodiment, the single-crystal silicon thin-filmtransistor 16 a is formed before the formation of the non-single-crystalsilicon thin film (polysilicon silicon thin film) 5′. With thisarrangement, it is possible to connect the single-crystal siliconsubstrate while keeping the flatness of the insulating substrate 2, andhence problems such as alignment failure can be prevented.

Note that, in the present embodiment, when the energy for implanting thehydrogen ions is increased in order to cause the peak position of thehydrogen atoms to be farther from the surface and the thickness of thesingle-crystal silicon thin film 14 a is caused to be thicker, noparticular changes are observed when the thickness is increased to be 50nm-100 nm. However, when the thickness is increased to be 300-600 nm, anS-value of the TFT is gradually increased so that the off-current isgreatly increased. Thus, depending on the doping density of theimpurities, the thickness of the single-crystal silicon thin film 14 ais generally not more than 600 nm, preferably about not more than 500nm, and more preferably not more than 100 nm.

Here, the energy for implanting the hydrogen ions is arranged in such amanner that, the energy for implanting the hydrogen ions is arranged sothat the energy after subtracting the energy corresponding to aprojection range of the hydrogen ions in a gate electrode material for agate electrode thickness from an incident energy of the hydrogen ions isno more than the energy corresponding to a projection range of theheaviest ions of gate constituent materials for a gate oxide thickness.

With this arrangement, for instance, it is possible to prevent thefollowing problem of the dent in characteristics and credibility: in theMOS single-crystal silicon thin-film transistor, the hydrogen ionsirradiated to the single-crystal silicon substrate collide with atomsconstituting the materials of the gate electrodes and metal wirings, sothat the atoms constituting the materials of the gate electrodes areflicked off and pass through the oxidized film, and eventually reach thesingle-crystal silicon and contaminate the same.

Also, when code 7059 (barium-borosilicate glass) of Corning® is adoptedas the insulating substrate 2 instead of code 1737 (alkaline-earthalumino-borosilicate glass) of Corning®, although the bonding itself canbe performed, the success rate of the cleavage stripping decreases.

This is because, as FIG. 8 shows, while the difference of linearexpansion between code 1737 and silicon when the temperature isincreased from substantially room temperatures to 600° C. is about 250ppm, the difference of linear expansion between code 7059 and silicon onequal terms is about 800 ppm.

Thus, taking into consideration of the success rate of the cleavagestripping, the difference of linear expansion between the insulatingsubstrate and silicon at temperatures between room temperatures and 600°C. is preferably not more than 250 ppm.

Note that, the single-crystal silicon thin-film transistor 16 a is notnecessarily limited to the arrangement having been described in thepresent embodiment. For instance, it is possible to obtain effectssimilar to the above by adopting a bottom gate MOS thin-film transistor.

Embodiment 2

The following will describe another embodiment of a single-crystalsilicon substrate, a semiconductor device, and a method of manufacturingthe same, in accordance with the present invention. FIGS. 2( a)-2(i) arecross sections illustrating a manufacturing process of the semiconductordevice of said another embodiment of the present invention. By the way,members having the same functions as those described in Embodiment 1 aregiven the same numbers, so that the descriptions are omitted for thesake of convenience.

Being identical with the above-described semiconductor device 20 ofEmbodiment 1, a semiconductor device 30 of the present embodiment isarranged in such a manner that, a MOS single-crystal silicon thin-filmtransistor 16 a and a non-single-crystal silicon thin-film transistor 1a are formed in different areas of an insulating substrate 2. Thus, thesemiconductor device 30 of the present embodiment is alsohigh-performance and highly functional, as the semiconductor device 20of Embodiment 1 is.

However, the semiconductor device 30 is different from the semiconductordevice 20 to the extent that, in the semiconductor device 30, thesingle-crystal thin-film transistor 16 a is formed after the formationof the non-single-crystal silicon thin-film transistor 1 a.

In the semiconductor device 30 of the present embodiment, members suchas a SiO₂ film 3, the non-single-crystal silicon thin-film transistor 1a, the single-crystal silicon thin-film transistor 16 a, and a metalwiring 22 are provided on the insulating substrate 2.

The non-single-crystal silicon thin-film transistor 1 a includes anon-single-crystal silicon thin-film 5′, a SiO₂ film 7 as a gateinsulating film, and gate electrodes 6. The single-crystal siliconthin-film transistor 16 a is, as described above, formed on theinsulating substrate 2 on which the non-single-crystal silicon thin-film1 a is formed, via an interlayer insulating film 7.

A single-crystal silicon substrate 10 a for forming the single-crystalsilicon thin-film transistor 16 a is subjected to a process for forminga MOS single-crystal silicon thin-film transistor, before the substrate10 a is provided on the insulating substrate 2. More specifically, thegate electrodes and gate insulating film are formed, impurity ions areimplanted into the source and drain, and channel injection is performedwith respect to P-type and N-type channel parts. Since a P-type siliconsubstrate is adopted in the present case, the channel injection to anN-type TFT is omitted. On the gate electrodes, an interlayer planarizedfilm is formed so as to have a predetermined shape, i.e. in the presentcase a SiO₂ formed by CVD and a BPSG which has been deposited, meltedand then planarized by CMP are formed so as to have predeterminedshapes. Then the single-crystal silicon substrate 10 a on which a MOSsingle-crystal silicon thin-film transistor 14 a is formed is washedusing a SC1 cleaning liquid so that particles are removed and thesurface is activated. Subsequently, under visible light, an aligningmark on the single-crystal silicon and an aligning mark on thetransparent substrate are detected through the glass substrate at roomtemperatures, and then the single-crystal silicon substrate 10 a isbonded to the insulating substrate 2. Here, the gate length isdetermined to be 0.35 μm, and as to the manufacturing rules of thecontact and metal wiring, the line width and space width are determinedto be 2 μm (micron) in order to correspond to the precision ofphotolithography on a large glass substrate and the precision of thealignment on the occasion of the bonding.

In the semiconductor device 30 of the present embodiment, the MOStransistors are formed in both of the area of the non-single-crystalsilicon thin film 5′ and the area of the single-crystal silicon thinfilm 14 a. Further, in the areas on which the transistors of the sameconductive type are formed, at least one of the mobility, subthresholdfactor, and threshold value varies from one area to another. Thus, inorder to obtain desired characteristics, it is possible to suitably formthe transistor either in the area of the single-crystal silicon or inthe area of the non-single-crystal silicon thin film.

The following will describe a method of manufacturing the semiconductordevice 30, with reference to FIGS. 2( a)-2(i).

First, as the insulating substrate 2, code 1737 (alkaline-earthalumino-borosilicate glass) of Corning® is adopted. Then as FIG. 2( a)shows, on the surface of the insulating substrate 2, a SiO₂ film 3 whichis about 100 nm thick is deposited by plasma CVD (Plasma Chemical VaporDeposition; hereinafter, this will be referred to as P-CVD at times)using a gas in which TEOS (Tetra Ethoxy Silane, i.e. Si(OC₂H₅)₄) ismixed with O₂ (oxygen).

Further, on the surface where the SiO₂ film 3 having been deposited, anamorphous silicon film 5 which is about 50 nm thick is deposited byplasma CVD using a SiH₄ gas.

Subsequently, as FIG. 2( b) illustrates, excimer laser is applied to theamorphous silicon film 5 in order to heating and crystallizing the same,so that an amorphous silicon layer is developed and thenon-single-crystal silicon thin film 5′ is formed. Note that, since theheating of the amorphous silicon film 5 is not necessarily carried outby applying the excimer laser, the heating may be carried out byapplying other types of laser or using a furnace. Also, to precipitatethe development of the crystal, at least one substance selected from thegroup of nickel, platinum, tin, and palladium may be added to theamorphous silicon film 5′.

Then, as FIG. 2( c) illustrates, a predetermined area of thenon-single-crystal silicon thin film 5′ is removed by etching.

Next, As FIG. 2( c) shows, for forming a non-single-crystal silicon (inthis case polycrystalline silicon or continuous grain silicon) TFT, aSiO₂ film 7 as a gate insulating film which is 80-100 nm thick isdeposited by plasma CVD using a SiH₄ gas and a N₂O gas, and then gateelectrodes 6 are formed.

Subsequently, as FIG. 2( d) illustrates, impurity ions for the sourceand drain are implanted, and then a SiO₂ film 4 which is about 250 nmthick is deposited thereon as an interlayer insulating film, by plasmaCVD using a gas in which TEOS Si(OC₂H₅)₄) is mixed with O₂ (oxygen).

Here, as in the case of the semiconductor device 20 of Embodiment 1, thesemiconductor device 30 of the present embodiment is arranged in such amanner that the single-crystal silicon substrate 10 a, on which aprocess for manufacturing a transistor to be the MOS single-crystalsilicon thin-film transistor 16 a is partly completed, is manufacturedby performing steps such as the implantation of hydrogen ions.

Then the shape of this single-crystal silicon substrate 10 a is cut bydicing or anisotropic etching using KOH so that the size of thesingle-crystal silicon substrate 10 a becomes slightly smaller than thesize of the predetermined area of the non-single-crystal silicon thinfilm 5′, from which an unnecessary part has been removed by etching.

The part from which the non-single-crystal silicon thin film has beenremoved in order to bond crystalline silicon thereto is planarized inadvance by GCIB (Gas Cluster Ion Beam) using a gas including low-energy(about 3 keV) halide. To further improve the bonding characteristics, aSiO₂ film which is about 10 nm is formed on the part by PECVD using TEOSor TMCTS (Tetramethylcyclotetrasiloxane).

The insulating substrate 2 on which the non-single-crystal silicon thinfilm 5′ is formed and the single-crystal silicon substrate 10 a arewashed using an SC1 liquid in order to remove particles and activate thesurfaces of the substrates, and then, as FIG. 2( e) illustrates, at roomtemperatures, a side of the single-crystal silicon substrate 10 a, theside being close to the dense position 15, is aligned with the areawhich has been etched as above, and subsequently, the single-crystalsilicon substrate 10 a and the area are caused to be intimately incontact with each other so as to be bonded with each other, in the wayidentical with the case of Embodiment 1. Here, the SC1 washing, which isone type of an washing method termed RCA, is carried out using a washingliquid made of ammonia, hydrogen peroxide, and pure water.

By the way, the formation of the single-crystal silicon substrate 10 aon the insulating substrate 2 may be carried out after the formation ofthe SiO₂ film 7 as the gate insulating film and before the deposition ofthe SiO₂ film 4 as the interlayer insulating film.

Then the single-crystal silicon substrate 10 a is subjected to heattreatment at temperatures of 300-600° C., in this case about 550° C., sothat the temperature of the dense position 15 of the single-crystalsilicon substrate 10 a is increased to be not less than the temperatureof hydrogen dissociation from the single-crystal Si. With thisarrangement, it is possible to carry out cleavage stripping at the denseposition 15 as a border. Incidentally, the heating treatment may becarried out in such a manner that, the temperature of the dense position15 of the single-crystal silicon substrate 10 a is increased by applyinglaser thereto or by means of lamp annealing in which a peak temperatureis not less than 700° C.

Then a damaged layer on the surface of the singe-crystal siliconsubstrate 10 a, which is left on the insulating substrate 2 as a resultof the stripping, is removed by lightly etching the same for about 10nm, by anisotropic plasma etching or wet etching, in the present casewet etching using buffer hydrofluoric acid. As a result, as FIG. 2( f)shows, the non-single-crystal silicon thin film 5′ and thesingle-crystal silicon thin film 14 a which are both about 50 nm thickare provided on one single insulating substrate 2. Note that, providedthat after the bonding of the single-crystal silicon substrate 10 a tothe insulating substrate 2 at room temperatures, heat treatment attemperatures of 300-350° C. for about 30 minutes is carried out and thenheat treatment at a temperature about 550° C. is carried out, theoccurrence of peeling on the occasion of the cleavage strippingdecreases.

At this point, the adhesive strength between the silicon and thesubstrate has already been sufficient. However, to further improve theadhesive strength, lamp annealing at a temperature about 800° C. isperformed for one minute. This lamp annealing may be performedsimultaneously with the activation of the impurities implanted to thesource and drain.

Subsequently, as is the case with Embodiment 1, a SiO₂ film 8 isdeposited as an interlayer planarized insulating film as FIG. 2( g)illustrates, a contact hole 21 is perforated as in FIG. 2( h), and thena metal wiring 22 is formed as in FIG. 2( i).

As described above, in the method of manufacturing the semiconductordevice of the present embodiment, the single-crystal silicon thin-filmtransistor 16 a is formed after the formation of the non-single-crystalsilicon thin-film transistor 1 a, so that the manufacturing process canbe simplified compared with the semiconductor device 20 of Embodiment 1in which the single-crystal silicon thin-film transistor is formedbefore the formation of the non-single-crystal silicon thin-filmtransistor, and hence, according to the present embodiment, themanufacturing process can be simplified and the contamination of thesingle-crystal silicon thin film can be prevented.

Embodiment 3

The following will describe a further embodiment of a single-crystalsilicon substrate, a semiconductor device, and a method of manufacturingthe same, in accordance with the present invention. FIGS. 3( a)-3(f) arecross sections illustrating a manufacturing process of the semiconductordevice of the present embodiment. By the way, members having the samefunctions as those described in Embodiments 1 and 2 are given the samenumbers, so that the descriptions are omitted for the sake ofconvenience.

As is the case with Embodiment 1, a semiconductor device 40 of thepresent embodiment is, as shown in FIG. 3( f), arranged such that anon-single-crystal silicon thin-film transistor and a single-crystalsilicon thin-film transistor are formed on a single insulating substrate2. While the present embodiment is identical with Embodiment 1 to theextent that the single-crystal silicon thin-film transistor is formedbefore the formation of the non-single-crystal silicon thin-filmtransistor, these embodiments are different from each other to theextent that, in the present embodiment, the single-crystal siliconthin-film transistor is a bipolar single-crystal silicon thin-filmtransistor, rather than a MOS single-crystal silicon thin-filmtransistor.

In this manner, it is possible to obtain the semiconductor device 40having characteristics different from the characteristics of thesemiconductor devices 20 and 30 described in Embodiments 1 and 2, byforming a MOS transistor as a non-single-crystal silicon thin-filmtransistor and a bipolar transistor as a single-crystal siliconthin-film transistor.

Here, the bipolar thin-film transistor is a transistor which is arrangedin such a manner that, a narrow reverse-conducting layer (base) isprovided between a collector and emitter of a first conducting-typesemiconductor, the number of minority carriers flowing from the emitterto base is controlled by inverting the bias between the emitter andbase, and consequently the current caused by the minority carriersflowing into the collector is controlled by changing bias of base.

Unlike MOS transistors, no gate electrodes are formed in the bipolarthin-film transistor so that the structure can be simplified and theproduction yield can be improved. Further, since the linearity in asaturation area is good and the reaction velocity is quick and hencelinear signal processing can be performed, the bipolar thin-filmtransistor can be adopted to devices such as an analog amplifier, acurrent buffer, and a power-supply IC.

Note that, in the bipolar single-crystal silicon thin-film transistor,the wiring rule of its contact pattern is more relaxed than the wiringrule of the base pattern.

With this arrangement, at least a part of the metal wiring of thesemiconductor device, in which the bipolar single-crystal siliconthin-film transistor is formed, can be processed simultaneously with themetal wiring on a large substrate, and this makes it possible to reducecosts and improve processing power. Further, since the connection to anexternal wiring, other circuit blocks, and TFT array becomes easy, theconnection failure is reduced so that the rejection rate is improved.

As FIG. 3( f) illustrates, the semiconductor device 40 is arranged suchthat the SiO₂ film 3, the non-single-crystal silicon thin-filmtransistor 1 a including the non-single-crystal silicon thin film 5′made of polycrystalline silicon, the bipolar single-crystal siliconthin-film transistor 16 b including the single-crystal silicon thin film14 b, and the metal wiring 22 are formed on the insulating substrate 2.

Since the MOS non-single-crystal silicon thin-film transistor 1 a andthe bipolar single-crystal silicon thin-film transistor 16 b are formedon one insulating substrate 2 as described above, it is possible toobtain the semiconductor device 40 by taking advantage of thecharacteristics of the MOS non-single-crystal silicon thin-filmtransistor and bipolar single-crystal silicon thin-film transistor, andthus the semiconductor device 40 can be adopted for various uses.

Now, a method of manufacturing the semiconductor device 40 will bedescribed with reference to FIGS. 3( a)-3(f).

First, as the insulating substrate 2, code 1737 (alkaline-earthalumino-borosilicate glass) of Corning® is adopted. Then as FIG. 3( a)shows, on the surface of the insulating substrate 2, a SiO₂ film 3 whichis about 20 nm thick is deposited by plasma CVD using a gas in whichTEOS is mixed with O₂.

Here, in the semiconductor device 40 of the present embodiment, as inthe cases of the semiconductor devices 20 and 30 in Embodiments 1 and 2,a single-crystal silicon substrate 10 b is arranged in advance in such amanner that a bipolar single-crystal silicon thin-film transistor 16 bis readily formed when cleavage stripping is performed at a denseposition 15 of implanted hydrogen ions as a border, and thesingle-crystal silicon substrate 10 b having been arranged in thismanner is bonded to an insulating substrate 2.

More specifically, first, a junction part of the bipolar thin-filmtransistor, which is for either PNP junction or NPN junction, is formed.Then the surface is oxidized or an oxide film is deposited thereon sothat a SiO₂ film 13 which is about 200 nm thick is formed. On thisaccount, the bipolar single-crystal silicon thin-film transistor, whichhas a dense position 15 of implanted hydrogen ions to which hydrogenions having a doze amount of 5×10¹⁶/cm² are implanted for apredetermined depth by a predetermined energy, is formed.

In this manner, the bipolar single-crystal silicon thin-film transistor16 b also has the dense position to which a predetermined concentrationof hydrogen ions is implanted for a predetermined depth, as in the caseof the MOS transistor.

Subsequently, the single-crystal silicon substrate 10 b, which has beenproperly shaped in advance, is formed on the insulating substrate 2.

After the insulating substrate 2 and properly-shaped single-crystalsilicon substrate 10 b are washed using a SC1 liquid and activated, asFIG. 3( b) illustrates, a side of the single-crystal silicon substrate16 b, the side being close to the dense position 15, is aligned with anarea on the insulating substrate 2, the area having been subjected tothe removal of an unnecessary part by etching. After performing thisalignment at room temperatures, the single-crystal silicon substrate 16b and the insulating substrate 2 are caused to be closely in contactwith each other so as to be bonded with each other at room temperatures.

The semiconductor device 40 of the present embodiment adopts, as FIG. 4shows, a laterally-structured bipolar thin-film transistor in whichimpurity ions are implanted into P and N areas and a collector 25, abase 26, and an emitter 27 are provided in one plane. However, thesemiconductor device 40 may adopt a conventional vertically-structuredthin-film transistor. Further, the junction may be formed by diffusingimpurities, and instead of the thin-film transistor, a SIT (StaticInduction Transistor) or a diode may be adopted in a similar manner.

Note that, however, since the present embodiment forms alaterally-structured bipolar thin-film transistor so as to realize theelimination of a planarizing process performed before the formation ofthe bipolar thin-film transistor, the manufacturing process can besimplified and the production efficiency can be improved.

Subsequently, heat treatment at temperatures of 400-600° C., in thiscase at a temperature about 550° C. is carried out so that thetemperature of the dense position 15 of the single-crystal siliconsubstrate 10 b is increased to be not less than the temperature ofhydrogen dissociation from the single-crystal silicon, and this makes itpossible to carry out cleavage stripping of an unnecessary part 11 ofthe single-crystal silicon substrate 10 b, at the dense position 15,thereby manufacturing the bipolar single-crystal silicon thin-filmtransistor 16 b on the insulating substrate 2.

Then a damaged layer on the surface of the singe-crystal siliconsubstrate 10 b, which is left on the insulating substrate 2, is removedby carrying out isotropic plasma etching or wet etching, in this case bylightly etching for about 20 nm by wet etching using buffer hydrofluoricacid. As a result, as FIG. 3( c) shows, the bipolar single-crystalsilicon thin-film transistor 16 b which is about 80 nm thick is formedon the insulating substrate 2.

Subsequently, as FIG. 3( d) illustrates, a SiO₂ film 4 which is about200 nm thick is formed as an interlayer insulating film on the entiresurface of the insulating substrate 2, by plasma CVD using a gas inwhich SiH₄ is mixed with N₂O. Further, as FIG. 3( d) illustrates, anamorphous silicon film 5 which is about 50 nm thick is formed over theSiO₂ film 4 by plasma CVD using a SiH₄ gas.

Next, as FIG. 3( e) illustrates, the amorphous silicon film 5 iscrystallized by applying excimer laser thereto so as to heat the film 5,and as a result, a polycrystalline silicon layer is developed and anon-single-crystal silicon thin film 5′ is formed. On this occasion, theadhesive strength between the bipolar single-crystal silicon thin-filmtransistor 16 b and the insulating substrate 2 may be enhanced.

Then, as FIG. 3( f) shows, an unnecessary part of the polycrystallinesilicon film 5′ is removed in order to cause a part, which becomes anactive area of the device, to be left, and consequently an island-shapedpattern is obtained. Subsequently, a SiO₂ film 7 which is about 350 nmthick is deposited as a gate insulating layer by plasma CVD using a gasin which TEOS is mixed with oxygen. Then after providing a photo-resistas a resin planarized film, which is about 350 nm, on the entiresurface, the entire surface of the resin planarized film and a part ofthe SiO₂ film 4 are etched by RIE (Reactive Ion Etching) which isanisotropic etching using a gas including oxygen and CF₄ (this etchingstep is not illustrated), and after the planarization, a SiO₂ film 7which is about 60 nm thick is formed as a gate insulating film, byplasma CVD using a gas in which SiH₄ is mixed with N₂O.

Then gate electrodes 6 are formed on the SiO₂ film 7, and consequentlythe non-single-crystal silicon thin-film transistor 1 a including thegate electrodes 6, the SiO₂ film 7 as a gate insulating film, and thenon-single-crystal silicon thin film 5′ are provided.

The subsequent steps such as the formation of a SiO₂ film 8 as aninterlayer planarized insulating film, the perforation of a contact hole21, and the formation of a metal wiring 22 are identical with the stepsin Embodiments 1 and 2, and thus omitted here.

As described above, the method of manufacturing the semiconductor device40 of the present embodiment is arranged such that, after the bipolarsingle-crystal silicon thin-film transistor 16 b is formed, thenon-single-crystal silicon thin-film transistor 1 a made of thepolycrystalline silicon thin film is formed. This arrangement makes itpossible to readily bond the bipolar single-crystal silicon thin-filmtransistor 16 b with the flat insulating substrate 2, and hence thebonding step can be simplified and the adhesive strength between thebipolar single-crystal silicon thin-film transistor 16 b and the flatinsulating substrate 2 can be improved.

Further, since the single-crystal silicon thin-film transistor in thepresent embodiment is bipolar type, the planarization step isunnecessary and thus the manufacturing costs can be reduced. Moreover,as in the case of the MOS transistor, the bipolar single-crystal siliconthin-film transistor may be arranged such that a part of the metalwiring is formed before the planarization step is carried out, and thismakes it possible to further increase the degree of integration.

Incidentally, in the semiconductor device 40 of the present embodiment,a group of transistors are not separated from each other, as in FIG. 3(f). If problems such as a leak current or the cross talk between theelements occur, it is possible to separate the elements from each other,as a matter of course.

Embodiment 4

The following will describe yet another arrangement of a single-crystalsilicon substrate, a semiconductor device, and a method of manufacturingthe same, in accordance with the present invention. FIGS. 5( a)-5(f) arecross sections illustrating a manufacturing process of the semiconductordevice of said yet another arrangement of the present invention. By theway, members having the same functions as those described in Embodiments1-3 are given the same numbers, so that the descriptions are omitted forthe sake of convenience.

A semiconductor device 50 of the present embodiment is identical withthe semiconductor device 20 of Embodiment 1 to the extent that a MOSsingle-crystal silicon thin-film transistor and a MOS non-single-crystalsilicon thin-film transistor are formed on one insulating substrate 2.On the contrary, the semiconductor device 50 is different from thesemiconductor device 20 to the extent that the semiconductor device 50adopts a continuous grain silicon as a non-single-crystal silicon thinfilm.

In this manner, using the continuous grain silicon as thenon-single-crystal silicon thin film makes it possible to obtain anon-single-crystal silicon thin-film transistor 1 b whosecharacteristics are better than the characteristics of anon-single-crystal silicon thin-film transistor made of polycrystallinesilicon.

In the semiconductor device 50 of the present embodiment, a SiO₂ film 3,a MOS non-single-crystal silicon thin-film transistor 1 b, and a MOSsingle-crystal silicon thin-film transistor 16 a are provided on theinsulating substrate 2.

In particular, the non-single-crystal silicon thin-film transistor 1 bis formed using polycrystalline silicon in which the crystal axis areuniform, i.e. using so-called continuous grain silicon as anon-single-crystal silicon thin film 52′.

Incidentally, while an N-channel TFT formed in the area of aconventional continuous grain silicon has mobility of about 200cm²/V·sec, an N-channel TFT formed in the area of a single-crystalsilicon thin film 14 a in an active matrix substrate for liquid crystaldisplaying, on the active matrix substrate the semiconductor device 50of the present embodiment being formed, has mobility of about 550cm²/V·sec. This proves that the present embodiment makes it possible tomanufacture an active matrix substrate which can respond quicker than aconventional active matrix substrate.

In this active matrix substrate for liquid crystal displaying, while notonly a driver but also devices formed in the area of thenon-single-crystal silicon thin film 52′ require a signal and powersupply voltage of 7-8V, a timing controller which is a device formed inthe area of the single-crystal silicon thin film 14 a stably operateswith the supply of a signal and power-supply voltage of 2.7V.

Now, the manufacturing process of the semiconductor device 50 will bedescribed in reference to FIGS. 5( a)-5(f).

In the present embodiment, as in the case of Embodiment 1, code 1737(alkaline-earth alumino-borosilicate glass) of Corning® is adopted asthe insulating substrate 2, and as FIG. 5( a) shows, on the entiresurface of the insulating substrate 2, a SiO₂ film 3 which is about 100nm thick is deposited by plasma CVD using a gas in which TEOS is mixedwith O₂.

Further, as FIG. 5( b) shows, on the entire surface of SiO₂ film 3, anamorphous silicon thin film 51 which is about 50 nm thick is depositedby plasma CVD using a SiH₄ gas. Then on the entire surface of the film51, a SiO₂ film 52 which is about 200 nm is deposited by plasma CVDusing a gas in which SiH₄ is mixed with N₂O.

After an opening section is formed in a predetermined area of the SiO₂film 52 by etching, an oxidized film (SiO₂ film) is formed by thinlyoxidizing the surface of the amorphous silicon thin film 51 at theopening section, in order to control the hydrophilicity of the surface.Further, the surface having been thinly oxidized is spin-coated by anickel acetate aqueous solution.

Next, as a result of solid phase crystallization at a temperature of580° C. for about 8 hours, polycrystalline silicon in which the crystalaxis are uniform, i.e. so-called continuous grain silicon is developedso that a continuous grain silicon thin film 51′ is formed.

Further, as FIG. 5( c) illustrates, the SiO₂ film 52 on the continuousgrain silicon thin film 51′ is removed. Subsequently, a predeterminedarea of the continuous grain silicon thin film 51′ is removed byetching.

Here, as in the case of Embodiment 2, the surface is planarized by GCIB(Gas Cluster Ion Beam) using a low-energy (about 3 keV) halide gas, sothat the bonding characteristics are improved. As in the case ofEmbodiment 1, the semiconductor device 50 of the present embodiment isalso arranged such that a part which becomes a MOS single-crystalsilicon thin-film transistor by being subjected to cleavage and thinningis manufactured in advance so that a single-crystal silicon substrate 10a to which hydrogen ions are implanted by applying predetermined energyis prepared.

Then, as FIG. 5( d) shows, after the insulating substrate 2 on which thecontinuous grain silicon thin film 51′ is formed and the single-crystalsilicon substrate 10 a are washed using a SC1 liquid and activated, aside of the single-crystal silicon substrate 10 a, the side being closeto the dense position 15, is aligned with an area on the insulatingsubstrate 2, the area having been subjected to the removal by etching.After performing this alignment at room temperatures, the single-crystalsilicon substrate 10 a and the insulating substrate 2 are caused to beclosely in contact with each other so as to be bonded with each other.

On this occasion, the distance between the continuous grain silicon thinfilm 51′ and the single-crystal silicon substrate 10 a is at least 0.3μm, preferably not less than 0.5 μm. With this arrangement, it ispossible to prevent metal elements such as nickel, platinum, tin, andpalladium, which are used in the subsequent manufacturing process, frombeing diffused to the single crystal silicon thin film 14 a, therebystabilizing the characteristics of the single-crystal silicon thin-filmtransistor.

Subsequently, the temperature of the dense position 15 of thesingle-crystal silicon substrate 10 a is increased to not less than thetemperature of hydrogen dissociation from the single-crystal silicon, byapplying laser to the interface 15 or by means of lamp annealing inwhich a peak temperature is not less than 700° C., so that, as FIG. 5(e) shows, an unnecessary part 11 of the single-crystal silicon substrate10 a is subjected to cleavage stripping at the dense position 15 as aborder.

Then, a damaged layer of the signal-crystal silicon thin film 10 a,which has been left on the insulating substrate 2, is removed by lightlyetching the same for about 10 nm, by anisotropic plasma etching or wetetching, in the present case wet etching using buffer hydrofluoric acid.

With this arrangement, it is possible to form the continuous grainsilicon thin film 51′ and the single-crystal silicon thin film 14 a,which are both about 50 nm thick, on the insulating substrate 2.

Subsequently, an unnecessary part of the continuous grain silicon thinfilm 51′ is removed by etching.

Then an opening section is formed on the SiO₂ film around the continuousgrain silicon thin film 51′, and in order to perform the gettering of Niwhich has been added for precipitating the development of crystal, usingthe SiO₂ film as a mask, concentrated P⁺ ions (15 KeV, 5×10¹⁵/cm²) areimplanted, and heat treatment at temperatures about 800° C. is performedfor one minute by RTA.

Note that, although a space is physically provided in order to preventthe diffusion of nickel atoms to the single-crystal silicon thin film 14a, small quantities of the nickel atoms are possibly diffused during theprocess. Thus, while an active area of the single-crystal silicon thinfilm 14 a is also preferably subjected to the gettering, if theformation of the space takes priority, the gettering can be omitted.

Next, an unnecessary part of the continuous grain silicon thin film 51′and the single-crystal silicon thin film 14 a are removed by etching, sothat an island-shaped pattern, which becomes an active area of thedevice, is formed.

Subsequently, a SiO₂ film which is about 350 nm thick is deposited byP-CVD using a gas in which TEOS is mixed with oxygen, and after etchingthe island-shaped pattern with the SiO₂ film for about 400 nm by RIEwhich is anisotropic etching, a SiO₂ film 7 as a gate insulating filmwhich is about 60 nm thick is formed by plasma CVD using a gas in whichSiH₄ is mixed with N₂O.

On this occasion, side walls are formed at the respective end portionsof the single-crystal silicon thin film 14 a and the continuous grainsilicon thin film 51′.

The subsequent steps such as the formation of a SiO₂ film 8 as aninterlayer planarized insulating film, the perforation of a contact hole21, and the formation of a metal wiring 22 are identical with the stepsin Embodiments 1 and 2, and thus omitted here.

As described above, the method of manufacturing the semiconductor device50 of the present embodiment is arranged such that, after the formationof the polycrystalline silicon as a non-single-crystal silicon thinfilm, the single-crystal thin-film transistor 16 a is formed, andsubsequently the SiO₂ film 7 as a gate insulating film of thenon-single-crystal silicon thin-film transistor 1 b. With thisarrangement, it is possible to reduce the number of the SiO₂ films andhence simplify the manufacturing process.

Embodiment 5

The following will describe still another arrangement of asingle-crystal silicon substrate, a semiconductor device, and a methodof manufacturing the same, in accordance with the present invention.FIGS. 6( a)-6(h) are cross sections illustrating a manufacturing processof the semiconductor device of said still another arrangement of thepresent invention. By the way, members having the same functions asthose described in Embodiments 1-4 are given the same numbers, so thatthe descriptions are omitted for the sake of convenience.

A semiconductor device 60 of the present embodiment is identical withthe semiconductor device 40 of Embodiment 3 to the extent that a bipolarsingle-crystal thin-film transistor and a MOS non-single-crystal siliconthin-film transistor are formed on one insulating substrate 2.

On the contrary, the semiconductor device 60 is different from thesemiconductor device 40 of Embodiment 3 to the extent that, in thesemiconductor device 60, a bottom-gate transistor is formed as anon-single-crystal silicon thin-film transistor.

Until the step of performing cleavage stripping, a manufacturing processof the semiconductor device 60 of the present embodiment is identicalwith the manufacturing process of the semiconductor device 30 ofEmbodiment 2. Also, a semiconductor device to be manufactured by theprocess of the present embodiment is structured so as to be identicalwith the semiconductor device 30.

As FIG. 6( i) illustrates, the steps after the step of performingcleavage stripping are arranged as follows: After a part to be asingle-crystal device is separated, an interlayer insulating film isformed on the entirety, and gate electrodes 6 for providing an amorphoussilicon TFT and circuit are formed thereon. Further, a gate insulatingfilm 62 and a non-dope amorphous silicon 63 are formed thereon in theshape of islands, and moreover a N⁺ amorphous silicon thin film 64 and ametal wiring 65 for wires of the source and drain are formed.

Incidentally, although not being illustrated, for purposes such asliquid crystal displaying, a protective insulating film, a planarizedfilm, and a transparent conductive film for displaying are furtherdeposited thereon.

The following will describe a method of manufacturing the semiconductordevice 60 with reference to FIGS. 6( a)-6(h).

First, as FIG. 6( a) illustrates, code 1737 (alkaline-earthalumino-borosilicate glass) of Corning® is adopted as the insulatingsubstrate 2. Then on the entire surface of the insulating substrate 2, aSiO₂ film 3 which is about 50 nm thick is deposited by plasma CVD usinga gas in which TEOS is mixed with O₂.

Here, as in the case of the semiconductor device 40 of Embodiment 3, thesemiconductor device 60 of the present embodiment is also arranged suchthat a part 16 b which becomes a bipolar single-crystal siliconthin-film transistor when being subjected to cleavage and thinning ismanufactured in advance so that a single-crystal silicon substrate 10 bis prepared, and into this single-crystal silicon substrate 10 b, apredetermined concentration of hydrogen ions is implanted by apredetermined energy, and then the single-crystal silicon substrate 10 bis reshaped so as to have a predetermined size.

After the insulating substrate 2 and the single-crystal siliconsubstrate 10 b having been cut are washed by a SC1 liquid and activated,as FIG. 6( b) shows, a side of the single-crystal silicon substrate 10b, the side being close to the dense position 15, is aligned with apredetermined position, by a method identical with the method inEmbodiment 1. After performing this alignment, the single-crystalsilicon substrate 10 b and the insulating substrate 2 are caused to beclosely in contact with each other so as to be bonded with each other atroom temperatures. Although not being illustrated, a metal wiring may beformed on the single-crystal silicon substrate in advance, since thisarrangement makes it possible to realize higher level of integrationthanks to miniaturization.

Subsequently, heat treatment at temperatures of 400-600° C., in thiscase at a temperature of about 550° C. is carried out so that thetemperature of the dense position 15 of the single-crystal siliconsubstrate 10 b is increased to be not less than the temperature ofhydrogen dissociation from the single-crystal silicon, and thus, as FIG.6( c) shows, the single-crystal silicon substrate 10 b is subjected tocleavage stripping at the dense position 15 as a border. When the metalwiring has been formed in advance, a melting point of the metal wiringis higher than the above-described range of temperatures even if themetal wiring is made of aluminum alloy, if hillock formation isneglected, and hence it is unnecessary to change the manufacturingprocess.

Next, a part of the single-crystal silicon thin film 14 b, which is lefton the insulating substrate 2, is removed by etching, and hence thesingle-crystal silicon thin film 14 b is manufactured so as to beisland-shaped. Then a damaged layer on the surface of the film 14 b islightly etched for about 10 nm by isotropic plasma etching or wetetching, in the present case wet etching using buffered hydrofluoricacid.

On this account, a part of the MOS thin-film transistor made of thesingle-crystal silicon thin film 14 b which is about 50 nm thick isformed on the insulating substrate 2.

Subsequently, as FIG. 6( d) shows, on the entire surface of theinsulating substrate 2, a SiO₂ film (interlayer insulating film) 61which is about 200 nm thick is formed by plasma CVD using a gas in whichSiH₄ is mixed with N₂O.

Further, a TaN thin film is deposited on the entirety of the SiO₂ film61 by sputtering, and a predetermined pattern is manufactured therefromso that a wiring of a gate layer, such as gate electrodes 6 and gate buslines is formed.

Note that, the wiring of the gate layer does not have to be made of thematerials above, and hence various metals such as aluminum and aluminumalloy may be used for manufacturing the wiring, in consideration ofelectrical resistance, heat resistance, and subsequent manufacturingsteps, etc.

Then, as FIG. 6( e) shows, a silicon nitride film 62 which is about 200nm thick is formed as a gate insulating film, by plasma CVD using a SiH₄gas and a NH₃ gas. Subsequently, an amorphous silicon film 63 which isabout 50 nm is deposited thereon by plasma CVD using a SiH₄ gas, andfurther a N+ amorphous silicon film 64 which is P-doped by a SiH₄ gasand PH₃ mixed gas and about 30 nm thick is deposited thereon.

Next, as FIG. 6( f) illustrates, an island-shaped part of an amorphoussilicon film which is non-dope as well as P-doped, the part becomes atransistor, is formed by etching, and as FIG. 6( g) shows, a titaniumfilm as a metal film 65 for a source bus wiring is deposited bysputtering, and manufactured so as to be a predetermined pattern.

Note that, the metal film 65 for the source bus wiring is also notnecessarily made of titanium, and hence the metal film 65 may be made ofvarious metals such as aluminum and aluminum alloy, in consideration ofelectrical resistance, heat resistance, and subsequent manufacturingsteps, etc.

Then, as FIG. 6( h) shoes, a N⁺ layer in a predetermined area (to be achannel between the source and drain) of the island-shaped amorphoussilicon 63 (and a part of the non-dope layer) is (are) removed byetching so that an amorphous TFT is formed.

Then a silicon nitride film which is about 200 nm thick is depositedthereon as a protective insulating film, by plasma CVD using a SiH₄ gasand a NH₃ gas.

Subsequently, as in the manufacturing process of an active matrixsubstrate made of conventional amorphous silicon, for instance, a resininterlayer film and transparent electrodes for displaying are formed sothat an active matrix substrate for liquid crystal displaying is finallyobtained.

As described above, since the semiconductor device 60 of the presentembodiment adopts an amorphous silicon as the non-single-crystal siliconthin film, the manufacturing process of the non-single-crystal siliconfilm can be simplified and the costs of manufacturing the semiconductordevice 60 can be reduced. Further, since the amorphous silicon has acharacteristic of low off-current, the semiconductor device 60 can beadopted to devices such as a low-power consumption LCD.

Note that, although the non-single-crystal silicon thin-film transistor1 c adopts an amorphous silicon as the non-single-crystal silicon thinfilm, a polycrystalline silicon thin film or a continuous grain siliconthin film may be adopted as the non-single-crystal silicon thin film.

Further, since the non-single-crystal silicon thin-film transistor 1 cis arranged such that the gate electrodes 6 are provided on the side ofthe insulating substrate 2, i.e. the non-single-crystal siliconthin-film transistor 1 c adopts a bottom-gate structure, it is possibleto easily form the amorphous silicon and hence the productivity isimproved thanks to the simplification of the manufacturing process, andconsequently it is possible to reduce the manufacturing costs of thesemiconductor device.

Note that, although the non-single-crystal silicon thin-film transistor1 c of the present embodiment has the bottom-gate structure, thetransistor 1 c is not necessarily arranged as such, thereby being ableto be arranged such that a non-single-crystal silicon, a gate insulatingfilm, and a gate are provided in this order from a substrate.

As FIG. 7 shows, the respective semiconductor devices having beendescribed in Embodiments 1-5 may be formed as highly-functional circuitsection (including a high-speed DAC, a high-speed timing controller, animage processing circuit, etc.) 71 on an active matrix substrate 70including display sections 72. Further, it is possible to form a displaydevice by adopting the active matrix substrate 70 as a display panel.

Note that, in the single-crystal silicon thin-film transistors 16 a and16 b of Embodiments 1-5, a wiring layer made of high melting point metalmay be provided above the gate layer. More specifically, it is possibleto adopt the following arrangement: A wiring for a circuit whichrequires micro-fabrication is formed using TiW alloy, and after theformation of an interlayer insulating film by CVD or PECVD using TEOS aSiH₄ gas and a N₂O gas, planarization is performed by methods such asCMP, and then a predetermined concentration of hydrogen ions isimplanted to the planarized film by a predetermined energy.

In this manner, a single-crystal silicon thin-film transistor on which ametal wiring is formed in advance is formed on an insulating substrateand a metal wiring is further formed after the formation of an oxidefilm, so that a semiconductor device with a double-metal-wiringarrangement can be obtained and a functional circuit in which higherintegration is realized can be formed.

Here, the high melting metal for the metal wiring layer can be chosenfrom materials such as polycrystalline silicon, silicide of variousmetals, titanium, tungsten, molybdenum, titanium/tungsten, tantalumnitrate, and tantalum, on condition that the heat resistance against thetemperature of heat treatment on the occasion of the cleavage strippingof the single-crystal silicon substrate. When the cleavage stripping ofthe single-crystal silicon substrate is performed using laser light, theheat resistance does not have to be high as above.

Further, the present invention is not limited to the above-describedembodiments. Thus, for instance, the method of manufacturing thenon-single-crystal silicon, the material and thickness of the interlayerinsulating film, etc. may be realized by those means known to personsskilled in the art.

Moreover, the semiconductor device formed by single-crystal silicon isalso not limited to the MOS transistor and bipolar transistor, and hencethe semiconductor device may be formed by an SIT or diode.

For instance, the aforementioned single-crystal silicon thin-film deviceis preferably provided with a MOS single-crystal silicon thin-filmtransistor and (i) an image sensor including a Schottky/PN-junctiondiode or (ii) a CCD image sensor. A cross section in FIG. 20 illustratesan example of such a semiconductor device including a CCD image sensorand a PN-junction diode. In this manner, there is such a possiblearrangement that an image sensor 17 is formed by adopting asingle-crystal silicon thin film 14 c, and this image sensor 17 as wellas a MOS single-crystal silicon thin-film transistor (not illustrated)are formed in an insulating substrate 2. Here, a transfer gate 12 a ismade of materials identical with the materials of the MOS single-crystalsilicon thin-film transistor. With this arrangement, it is possible tointegrate differently-arranged or differently-structured thin-filmdevices in different areas, and hence CMOS devices such as an imagesensor and devices having structures different from those of the CMOSdevices can be integrated with ease, even if the coexistence of thesedevices has conventionally been extremely difficult, so thathighly-functional devices which have not been able to be manufacturedcan be created.

In this manner, one of the important benefit of the present invention issuch that different semiconductor devices having differentcharacteristics can be integrated on a single glass substrate.

Further, although the examples in above-described Embodiments 1-5 relateto two different silicon thin-film transistors having differentcharacteristics, the present invention is not limited to thisarrangement so that a semiconductor device of the present invention maybe arranged such that 3 or more devices having different characteristicsare formed on a single substrate.

For instance, in the case of a semiconductor device in which a MOStransistor and a bipolar transistor are formed as single-crystal siliconthin-film transistors and a MOS transistor is formed as anon-single-crystal silicon thin-film transistor, 3 semiconductor deviceshaving different characteristics can be formed on one substrate, andthus it is possible to obtain a semiconductor device having higherperformances and functions. An example of such a semiconductor device isshown in FIG. 19. This figure is equivalent to a cross sectionillustrating the step in the manufacturing process, shown in FIGS. 1( f)and 3(f).

In such a semiconductor device, a single-crystal silicon thin film of aMOS thin-film transistor made of single-crystal silicon is preferablythinner than a single-crystal silicon thin film of a bipolar thin-filmtransistor.

This is because, it has been known that generally thinner MOS thin-filmtransistors have better characteristics, and relatively thicker bipolarthin-film transistors have better characteristics.

Note that, in a MOS thin-film transistor made by a single-crystalsilicon thin film, the widths of gate lines are preferably not more than1 μm. Also, in a bipolar thin-film transistor made by a single-crystalsilicon thin film, the base width is preferably not more than 2.5 μm.

More preferably, the base width is not more than 1 μm. This is because,the narrower the base width is, the better the efficiency of diffusionand passage of the minority carriers, and hence time can be saved.

With this arrangement, it is possible to increase the speed of switchingthe transistor.

Embodiment 6

The following will describe still another arrangement of asingle-crystal silicon substrate, a semiconductor device, and a methodof manufacturing the same, in accordance with the present invention. Bythe way, members having the same functions as those described inEmbodiments 1-5 are given the same numbers, so that the descriptions areomitted for the sake of convenience.

In the present embodiment, the thickness of the single-crystal siliconsubstrate before bonding is about 70 μm, while, in Embodiments 1-5, thethickness of the single-crystal silicon substrate before bonding isabout 100 μm. Although the present embodiment and Embodiments 1-5 areidentically arranged except the thickness of the single-crystal siliconsubstrate before bonding, the present embodiment excels in the qualityof bonding between the glass substrate and silicon substrate, and inparticular, the alignment failure at the corners of the substrate isreduced.

Incidentally, in the present embodiment, the thickness is reduced afterthe implantation of hydrogen ions, by a grinding method used for ICcards. The thinner the thickness of the single-crystal silicon is, themore the bonding quality improves. However, taking the manageability ofthe single-crystal silicon into consideration, the thickness ispreferably within the range of about 50-100 μm.

Further, although all of Embodiments 1-6 describe a MOS transistor, thepresent invention is not limited to the transistor of this type. Thus,for instance, even if a MIS transistor other than the MOS transistor isadopted, the same effects can be obtained.

Here, the MIS transistor is a transistor which adopts a silicon nitridefilm as a gate insulating film, and since the electric field effects ofthis transistor is great due to the high permittivity of the gateinsulating film, the transistor can operate at low voltages even if aleak current of the gate increases.

Embodiment 7

The following will describe still another embodiment of the presentinvention.

In the above-described embodiments, after the formation of asemiconductor device structure on a single-crystal silicon substrate,the single-crystal silicon substrate is separated (separated) so that asingle-crystal silicon thin film is formed on an insulating substrate.However, the present invention is not limited to this arrangement. Thus,there is such a possible arrangement that a single-crystal siliconsubstrate on which a semiconductor device structure is not provided isseparated so that a single-crystal silicon thin film is provided on aninsulating substrate, and then a semiconductor device structure isformed on the single-crystal silicon thin film.

As FIG. 10 illustrates, an SOI (Silicon on Insulator) substrate 101 ofthe present embodiment is manufactured by bonding a light-transmittingsubstrate (insulating substrate) 102 with a single-crystal silicon thinfilm 105.

More specifically, on the light-transmitting substrate 102, an oxidizedsilicon film (insulating film) 103 is deposited. This light-transmittingsubstrate 102 is, for instance, a light-transmitting amorphousnon-alkali high strain point glass substrate, such as code 1737(alkaline-earth alumino-borosilicate glass) of Corning®. Further, thesingle-crystal silicon thin film 105 is covered with an oxidized siliconfilm (covering film) 104, and then a bonded interface (surface) wherethe oxidized silicon film 103 is bonded with the oxidized silicon film104 is formed. The steps for manufacturing the SOI substrate 101 will bedescribed below with reference to FIGS. 11( a)-11(g).

On the light-transmitting substrate 102 shown in FIG. 11( a), theoxidized silicon film 103 is formed. Thus, as FIG. 11( b) shows, theoxidized silicon film 103 is deposited on the light-transmittingsubstrate 102. The oxidized silicon film 103 is provided in this mannerbecause the water-wettability (hydrophilicity) of the light-transmittingsubstrate 102 is insufficient without the oxidized silicon film 103.

The thickness of the oxidized silicon film 103 is preferably within therange of about 40-300 nm, and is about 100 nm in this embodiment. Themethod of forming the film is not particularly limited. For instance, bya TEOS-O₂ plasma CVD method, a TEOS (Tetra Ortho Silicate) gas is mixedwith an oxygen gas in a vacuum chamber, and then the oxidized siliconfilm 103 which is about 100 nm thick is formed by plasma discharging ata temperature about 320° C.

Also, since the oxidized silicon film 103 is formed in thermallynon-equilibrium states at relatively low temperatures (300-400° C.), thecomposition ratio of silicon to oxygen is not exactly 1:2, and hence,the composition ratio is, for instance, 1:1.9. Thus, the oxidizedsilicon film 103 of the present embodiment is a so-called oxidizedsilicon film, i.e. a SiO₂ insulating film. Incidentally, when theoxidization is performed at a temperature about 900° C., the oxidizedsilicon film 103 is formed in thermally equilibrium states so that thecomposition ratio of silicon to oxygen is exactly 1:2.

On this occasion, the tangent of the maximum slope of themicro-roughness to the surface of the oxidized silicon film 103 and theflat surface of the substrate is not more than 0.06. More specifically,for instance, in respect of micro-roughness which is not more than 5 nmhigh and measured in a 1-5 μm square on the surface of the oxidizedsilicon film 103, the tangent of the maximum slope of themicro-roughness to the surface of the light-transmitting substrate 102is not more than 0.06. By the way, these micro-roughness on the surfacewill be discussed later.

Meanwhile, the single-crystal silicon thin film 105 as illustrated inFIG. 10 is manufactured from the single-crystal silicon substrate 106 asshown in FIG. 11( c).

The surface of the single-crystal silicon substrate 106 is subjected toheat treatment, and then covered with the oxidized silicon film 104 asin FIG. 11( d). The thickness of the oxidized silicon film 104 ispreferably 5-300 nm, and more preferably 40-300 nm. In the present case,the thickness is about 100 nm.

Next, as FIG. 11( e) illustrates, hydrogen ions indicated by arrows inthe figure are implanted into a predetermined interface (dense positionof implanted hydrogen ions) of the single-crystal silicon substrate 106.Here, as FIG. 11( e) shows, the dense position 110 is located at apredetermined depth from the surface.

Subsequently, as FIG. 11( f) illustrates, the light-transmittingsubstrate 102 in FIG. 11( c) is bonded with the single-crystal siliconsubstrate 106 in FIG. 11( e), after these substrates are washed using aSC1 liquid and dried. Now, the steps of washing and drying will bedescribed as below.

In the present embodiment, the light-transmitting substrate 102 on whichthe oxidized silicon film 103 is provided as a covering film is bondedwith the single-crystal silicon substrate 106 whose surface is oxidizedand covered by the oxidized silicon film 104, without using an adhesive.To perform this bonding, the condition, cleanliness, and degree ofactivity of the respective surfaces of the films are very importantfactors.

Note that, such bonding without using an adhesive is realized thanks tocontributions by van der Waals force, electric dipole, and hydrogenbond. The respective surfaces of the substrates are easily bonded witheach other especially when both of the surfaces are similarly arrangedin terms of the balance of the above-mentioned contributions.

First, the light-transmitting substrate 102 covered with the oxidizedsilicon film 103 and the single-crystal silicon substrate 106 whosesurface is oxidized and covered with the oxidized silicon film 104 arewashed using a SC1 liquid.

The SC1 liquid is made by mixing commercially-available ammonia water(NH₄OH: 30% solution), oxygenated water (H₂O₂: 30% solution), and purewater (H₂O) at a predetermined ratio. For instance, these waters aremixed at a ratio of 5:12:60.

Into this SC1 liquid, the light-transmitting substrate 102 and thesingle-crystal silicon substrate 106 are immersed for 10 minutes.

Note that, as “Ultra-Clean USLI Technology” (Tadahiro Omi; Baihukan;page 172) describes, the ammonia water slightly etches the surface ofoxidized silicon so that the immersion should not take long time.

Subsequently, the light-transmitting substrate 102 and thesingle-crystal silicon substrate 106 are rinsed by flowing pure waterfor 10 minutes, so that the washing step is completed, the resistivityof this pure water is, for instance, not less than 10 MΩcm. Then thesubstrates having been washed are quickly dried using devices such as aspin dryer, and consequently the light-transmitting substrate 102covered with the oxidized silicon film 103 and the single-crystalsilicon substrate 106 whose surface is oxidized and covered with theoxidized silicon film 104 are caused to be in touch with each other andbonded with each other.

Next, in order to form the single-crystal silicon thin film 105 byseparating the single-crystal silicon substrate 106, heat treatment bycarrying out annealing for 30 minutes by means of an electric furnace orby carrying out lamp annealing. Through this step, as FIG. 11( g) shows,a single-crystal silicon substrate 106 a is separated at a denseposition 110 of implanted hydrogen ions, so that the SOI substrate 101including the single-crystal silicon thin film 105 is formed. In thepresent case, the bonding quality at the bonded interface does notdeteriorate.

Note that, the thickness of the single-crystal silicon thin film 105 onthe surface of the SOI substrate 101 is preferably 300 nm. Also, thedirections of the surface of the single-crystal silicon thin film 105,the surface facing the substrate, are set so as to be (100), (110), and(111). With this arrangement, it is possible to obtain a sufficientlyflat mirror surface. In other words, it is possible to manufacture anSOI substrate having a flat silicon film surface which does not requirepolishing.

Now, referring to FIG. 12, the condition of the surface of the oxidizedsilicon film 103 illustrated in FIG. 11( b) will be described as below.

As FIG. 12 shows, the surface of the oxidized silicon film 103 on thelight-transmitting substrate 102 has micro-roughness. The image of thesurface in FIG. 12 indicates the data of the micro-roughness along aparticular line, the data being extracted from an AFM (Atomic ForceMicroscope) image of the surface of the oxidized silicon film 103.

In the oxidized silicon film 103 of the present embodiment, the maximumslope of the micro-roughness on the surface of the substrate 103 to thesurface of the substrate 103 is not more than 0.04. Here, the surface ofthe light-transmitting substrate 102 is in parallel with a dotted linein FIG. 12, which indicates zero-height.

When the oxidized silicon film 103 formed as above and thesingle-crystal silicon substrate 106 covered with the oxidized siliconfilm 104 are washed using the SC1 liquid, rinsed by pure water, driedand then caused to be in touch with each other, the oxidized siliconfilm 103 is bonded with the oxidized silicon film 104 by exerting littlestrength. On the occasion of the bonding, after exerting initialstrength, the films start to be autonomously bonded with each other.Hereinafter, this autonomous bonding will be termed autonomous bondingability.

Now, an example of a cross section of a conventionally-arranged oxidizedsilicon film on a substrate is shown in FIG. 16. In this example, anoxidized silicon film which is not less than 500 nm thick is formed on asubstrate. As the figure illustrates, the tangent of the maximum slopeof the micro-roughness to the surface and the surface of the substrateis not less than 0.06. Note that, in the present example, an absolutevalue (vertical variation with respect to the surface of the substrate)of the micro-roughness on the surface of the conventional oxidizedsilicon film is about not more than an absolute value of themicro-roughness on the surface of the oxidized silicon film 103 of thepresent embodiment, which is shown in FIG. 12.

In the present example, when the substrate on which the oxidized siliconfilm is deposited as in FIG. 16 is caused to be in touch with a piece ofsingle-crystal silicon, these members cannot properly be bonded witheach other. That is to say, when the tangent of the maximum slope of themicro-roughness on the surface to the surface of the substrate is notless than 0.06, the substrate and the piece of single-crystal silicon donot exert the autonomous bonding ability.

Note that, the oxidized silicon film 104 on the single-crystal siliconsubstrate 106 is formed in such a manner that a thermally-oxidized filmis formed on a flat single-crystal silicon substrate in thermallyequilibrium states. That is to say, for instance, sincecommercially-available single-crystal silicon substrates 106 aregenerally flat, the flatness when a covering film having a predeterminedthickness can be expected to some degree. The oxidized silicon film 104is flat to some extent, on condition that the thickness thereof is aboutnot more than 500 nm.

In this manner, even if measures against the deterioration of thebonding characteristics due to the micro-roughness on the surface, suchas the improvement of the condition of the washing before the bonding,are taken, it is not possible to obtain sufficient bondingcharacteristics. For this reason, problems such as peeling of thesingle-crystal silicon thin film on the occasion of the separationcannot be avoided. That is to say, in some cases, only performing theimprovement of the condition of the washing is not sufficient to preventthe occurrence of the problems.

Next, with respect to the substrate on which the oxidized silicon filmin which the tangent of the maximum slope of the micro-roughness is notless than 0.06 is formed, surface polishing by means of a CMP (ChemicalMechanical Polishing) method is conducted. This causes the tangent ofthe maximum slope of the micro-roughness on the oxidized silicon filmhaving been covered to the surface of the substrate to be not more than0.06, preferably not more than 0.04. In this case, the substrate onwhich the oxidized silicon film is deposited and the piece ofsingle-crystal silicon can be caused to be in touch with each other andthen bonded, without any problem.

Now, the water wettability of the light-transmitting substrate 102covered with the oxidized silicon film 103 of the present embodiment ismeasured after the washing using the SC1 liquid. More specifically, asFIG. 13 illustrates, a contact angle θ with respect to water W ismeasured using a contact angle measuring device.

Using the contact angle measuring device, an image of the water W at theinstant of the contact with the surface of the oxidized silicon film 103is taken for a cross-sectional observation. Here, an angle between atangent line (dotted line) along the end portion of the dropped water Wbeing in touch with the surface of the oxidized silicon film 103 and thesurface of the light-transmitting substrate 102 is set as the contactangle θ.

The light-transmitting substrate 102 and the dropped water W are at atemperature of 25° C. The contact angle θ is measured from the imagetaken immediately after the water W is in contact with the surface ofthe oxidized silicon film 103. An amount of the dropped water W is 1microliter, and as the water W, “Water for Injections” made by made byOtsuka Pharmaceutical Co., Ltd is adopted.

In the case of the light-transmitting substrate 102 which has themicro-roughness thereon as illustrated in FIG. 12 and covered with theoxidized silicon film 103 of the present embodiment, the contact angle θwith respect to the water W is not more than 10° after the washing usingthe SC1 liquid, and as described above, the tangent of the oxidizedsilicon film 103 to the maximum slope of the micro-roughness on thelight-transmitting substrate 102 is not more than 0.04.

Further, the wettability of the single-crystal silicon substrate 106which is oxidized and covered with the oxidized silicon film 104 is alsomeasured in a similar manner to the light-transmitting substrate 102.Also in this case, the contact angle θ with respect to the water W isnot more than 10° after the washing using the SC1 liquid.

Then, as in the foregoing description, after the oxidized silicon film103 and the oxidized silicon film 104 are dried and caused to be incontact with each other, these films are autonomously bonded with eachother, after exerting little force thereto.

Here, the adhesive strength (adhesive power) after the bonding can beestimated in the following manner: The adhesive strength can beevaluated by a test of peeling a bonded thin film from its end portion.According to “Theory of Elasticity”, E. M. Lifshitz and L. D. Landau(translated by Tsunezo Sato; Tokyo Tosho), when a thin film whosethickness is h is peeled off from an object by exerting an externalforce on the object against its surface tractive force, an adhesivestrength a per a unit length is expressed by the following equation.

α={Eh ³/24(1−σ²)}(∂² ζ/∂x ²)²

Here, E is Young's modulus of the thin film, σ is Poisson's ratio of thethin film, h is the thickness of the thin film, x is a lateral axis of aplane to which the thin film is adhered, and ζ is a displacement of afilm to be peeled off in the direction of the normal of the thin film. Aschematic cross section of this arrangement is shown in FIG. 17. As inthis figure, the thickness of a space at coordinates which are away fromthe end portion (x=0) of a contact face for a distance x in the lateraldirection is ζ, and ζ and x are variables. In FIG. 17, a tape Tfunctions to exert a force of peeling a thin film 29 off from an object28. That is to say, when the thin film 29 is peeled off from the object28 using the tape T, the differential equation of second order of thevariable ζ from the bonding surface of the thin film 29 contributes tothe adhesive strength. In this manner, it is possible to obtain theadhesive strength α by figuring out a coefficient of the partialdifferential equation of second order of the variable ζ in the normaldirection, with respect to the x-axis.

As FIG. 11( f) shows, provided that the light-transmitting substrate 102in which the tangent of the maximum slope of the micro-roughness on thesurface of the substrate to the surface is not more than 0.06 is bondedwith the single-crystal silicon substrate 106, the adhesive strengthmeasured by means of the above-described method is large, i.e. not lessthan 0.6 N/m.

In the meantime, when the tangent the maximum slope of themicro-roughness on the surface of the substrate to the surface of thesubstrate is not less than 0.06, the autonomous bonding ability is notobserved so that the adhesive strength is only about 0.2 N/m.

Note that, the evaluation of the adhesive strength is carried out afterthe bonding and before the enhancement of the adhesive strength bymethods such as heat treatment. Thus, by conducting heat treatment afterthe evaluation, it is possible to improve the adhesive strength forabout 10-1000 times. In this manner, the SOI substrate 101 of thepresent embodiment is arranged so that the adhesive strength thereof isnot less than 0.6 N/m, when measured before the bonding of the oxidizedsilicon film 103 with the oxidized silicon film 104 and after theenhancement of the adhesive strength by means of methods such as heattreatment. Thus, comparing to the case when heat treatment is performedwith respect to an SOI substrate whose adhesive strength is about 0.2N/m after the bonding, the SOI substrate 101 of the present embodimentafter the heat treatment has a greater adhesive strength.

Further, as in the foregoing description, the oxidized silicon film 103which is the covering film of the light-transmitting substrate 102 ismade at a temperature about 320° C. by a plasma chemical vapordeposition method using a gas in which a TEOS gas is mixed with anoxygen gas. That is to say, the oxidized silicon film 103 made by theplasma CVD method is easily bonded with the oxidized silicon film 104which is also a covering film.

In contrast, provided that the above-mentioned covering film is formedby applying an argon gas and an oxygen gas to a target oxidized silicon,i.e. formed by a RF reactive sputtering, the tangent of themicro-roughness is not less than 0.06, and the contact angle θ withrespect to water W is not less than 10°. In this case, when a substrateon which the covering film is deposited is caused to be in touch with apiece of single-crystal silicon, the film and the piece are not bondedwith each other by the autonomous bonding ability.

As described above, the SOI substrate 101 of the present embodiment isarranged such that the oxidized silicon film 103 in which the tangent ofthe maximum slope of the micro-roughness on the surface of the oxidizedsilicon film 103 to the surface of the light-transmitting substrate 102is not more than 0.06 is bonded with the oxidized silicon film 104 whichis a covering film.

Further, in the SOI substrate 101, the respective contact angles θ withrespect to water W are not less than 10° on the surface of the oxidizedsilicon film 103 and on the surface of the oxidized silicon film 104.

Moreover, in the SOI substrate 101, the oxidized silicon film 103 isformed by a plasma CVD method using a gas in which a TEOS gas is mixedwith an oxygen gas.

With these arrangements, it is possible to set the adhesive strengthbetween the oxidized silicon films 103 and 104 to be not less than 0.6N/m. Since the adhesive strength in the SOI substrate 101 is enhanced inthis manner, the peeling of the film does not occur, and thiselimination of the peeling makes it possible to improve the yield andreduce costs.

When bonding the oxidized silicon film 103 with the oxidized film 104,the conditions of the respective films, the cleanliness of the surfaces,and the degree of activity of the surfaces are important factors. Also,the bonding is realized thanks to contributions by van der Waals force,electric dipole, and hydrogen bond. The surfaces are easily bonded witheach other especially when the surfaces are similarly arranged in termsof the balance of the above-mentioned contributions, and the arrangementabove makes it possible to cause the balances of the contributions ofthe respective surfaces to be similar. On this account, it is possibleto improve the adhesive strength as above.

Now, the following will describe an example of an SOI substrate in whicha polycrystalline silicon film as well as a single-crystal silicon thinfilm are provided on an insulating substrate.

FIGS. 14( a)-14(h) are cross sections showing an example of the stepsfor manufacturing the SOI substrate. To manufacture the SOI substrate,first, on a light-transmitting substrate 102 in FIG. 14( a), an oxidizedsilicon film 113 as an insulating film is deposited as illustrated inFIG. 14( b).

Then, as FIG. 14( c) shows, an amorphous silicon film 114 is formed byapplying a monosilane gas, on the ground of plasma CVD.

Then, after performing dehydrogenation annealing, a part where apolycrystalline silicon TFT will be formed is melted by methods such asthe application of excimer laser as indicated by arrows in FIG. 14( d).Subsequently, the part having been melted is poly-crystallized so that apolysilicon film 114 a is formed as in FIG. 14(e).

Next, be means of photolithography, the silicon film is etched in orderto form a part where a piece of single-crystal silicon is placed, sothat a polysilicon film 114 b is removed. The remaining polysilicon film114 a is now regarded as a polysilicon area 112, as illustrated in FIG.14( f). After being subjected to washing using a SC1 liquid and rinsing,the substrate is dried.

In the meantime, the surface of a single-crystal silicon substrate 106is oxidized so that an oxidized silicon film 104 is formed thereon.Subsequently, hydrogen ions are implanted, washing by the SC1 liquid andrinsing are carried out, and then drying is performed. Subsequently, asFIG. 14( g) shows, the oxidized silicon film 104 of the single-crystalsilicon substrate 106 is bonded with the oxidized silicon film 113.

Subsequently, as in the above-mentioned embodiments, heat treatmentusing devices such as an electric furnace or lamp furnace is carriedout, and then, as FIG. 14( h) shows, the single-crystal siliconsubstrate 106 is stripped and separated at a dense position 110 ofimplanted hydrogen ions as a border, so that a single-crystal siliconthin film 105 is obtained.

Here, setting the thickness of the single-crystal silicon thin film 105to be identical with the thickness of the polysilicon area 112 isgreatly helpful for a process of manufacturing a TFT using thepolysilicon area 112 and the single-crystal silicon film 5.

In the present case, since the SOI substrate 111 manufactured as aboveis a light-transmitting substrate, the SOI substrate 111 can be easilyadopted to display devices. For instance, a thin-film transistor ismanufactured using the single-crystal silicon thin film 105, and thisthin-film transistor can be adopted to display devices such as a TFTliquid crystal display (LCD) device and a TFT organicelectro-luminescence (OLED: Organic Light Emitting Diode) displaydevice.

An example of such display devices will be described in reference toFIG. 18.

As FIG. 18 shows, a liquid crystal display device 131 includes a controlsection 132, a gate driver 133, a source driver 134, a liquid crystaldisplay panel 136 including a liquid crystal display section 135. Inthis example, the liquid crystal display panel 136 is an active matrixsubstrate (semiconductor device) manufactured by adopting theabove-mentioned SOI substrate 111.

In accordance with an image input signal supplied from the outside ofthe liquid crystal display device 131, the control section 132 transfersthe image signal, control signal, and clock signal to the gate driver133 and the source driver 134. The gate driver 133 outputs a gate drivesignal to the liquid crystal display panel 136. The source driver 134outputs signals of source bus lines to the liquid crystal display panel136.

In this manner, using the SOI substrate 111 as a display panel driven inan active matrix manner makes it possible to cause the characteristicsof a transistor to be uniform, stabilized, and improved. Further, thearrangement above allows systems such as active matrix drivers, aperipheral driver, and a timing controller to be further integrated.

Note that, the process of manufacturing a thin-film transistor (TFT) byadopting the SOI substrate 111 is identical with a conventional TFTprocess.

For instance, to manufacture a coplanar transistor, a silicon film ofthe SOI substrate 111 is caused to be island-shaped, and as FIG. 15shows, a gate insulating film 122 which is a SiO₂ insulating film isformed.

Then, after forming and patterning a gate electrode film 123, ionimplantation of phosphorus and boron is carried out so that a part of alow-resistance silicon film (n⁺ or p⁺ silicon film) 124 is obtained.After performing activation annealing by heat, an interlayer insulatingfilm 126 which is a SiO₂ insulating film is formed. A part which ismasked by the gate electrode film 123 is regarded as a channel area 125.

After forming a contact hole through the interlayer insulating film 126,a source/drain metal film 127 is formed and patterned.

In this manner, as FIG. 15 shows, it is possible to manufacture asingle-crystal silicon TFT or a partly-single-crystal silicon TFT, whichis a thin-film transistor 121.

In addition to the above, it is possible to provide a non-single-crystaldevice in the above-mentioned polysilicon area 112. By the way, insteadof the polysilicon area 112, an amorphous silicon thin film or acontinuous grain silicon thin film may be provided as anon-single-crystal thin film.

Further, after forming a semiconductor device structure as anon-single-crystal silicon device in the polysilicon area 112, asingle-crystal silicon thin film 105 may be provided so as to form asingle-crystal silicon device. Alternatively, after the formation of thesingle-crystal silicon thin film 105 on the substrate 102, anon-single-crystal thin film may be further provided on the substrate102.

It is needless to say that one can appropriately combine the presentembodiment with any one of Embodiments 1-6. That is to say, forinstance, the arrangement for improving the adhesive strength betweenthe insulating substrate and the single-crystal silicon thin film, whichhas been discussed in the present embodiment, may be combined with anyone of the above-mentioned arrangements of Embodiments 1-6.

As discussed above, among silicon semiconductors used for manufacturingICs and thin-film transistors, and among transistor devices manufacturedfrom the silicon semiconductors, the present invention relates tomaterials for manufacturing a transistor element in which (i) asingle-crystal silicon thin film or (ii) a single-crystal silicon thinfilm and a non-single-crystal silicon thin film is/are adopted, moreparticularly relates to an SOI substrate, a display device, and a methodof manufacturing the SOI substrate.

An integrated circuit element technology for forming and integratingelements such as a transistor on a substrate has been developed in linewith the diffusion of computers.

According to the technology, for instance, a single-crystal siliconsubstrate is manufactured so that several hundred million transistorsare formed on a substrate. More specifically, a commercially-availablesingle-crystal silicon wafer which is less than 1 mm thick and about 200mm in diameter is processed so that a great number of transistors areformed thereon.

Since an SOI substrate is adopted in the field of manufacturing ICs fordramatically improving the performances of a semiconductor element bymanufacturing good transistors, it is out of consideration whether ornot the substrate is transparent and whether or not the substrate iscrystalline, as long as the substrate is an insulating layer. In thefield, when a transistor is manufactured using the SOI substrate, anelement is completely separated so that the operations of the transistorare rarely limited and characteristics and performances thereof aregood.

In the meantime, when the SOI substrate is adopted to the display deviceof the present invention, it is, as described above, preferable that theSOI substrate is light-transmitting.

According to the arrangement of Japanese Laid-Open Patent ApplicationNo. 2000-30996, when a single-crystal silicon film is formed on alight-transmitting substrate by the steps of bonding, separating, andstripping, the size of a piece of single-crystal silicon is not alwaysidentical with the size of the glass substrate, and hence, in thepresent arrangement, the maximum diameter of the piece of single-crystalsilicon is 12 inches (300 mm). Thus, according to this arrangement, itis not possible to form a single-crystal silicon thin film on the entiresurface of the substrate.

In contrast, in the SOI substrate of the present invention, as in thecase of the above-described SOI substrate 1, it is possible to form asingle-crystal silicon thin film on a substantially entire surface of asubstrate.

Note that, the use of the semiconductor device and its manufacturingmethod in accordance with the present invention is not limited to aliquid crystal display device, and thus, it is needless to say that thesemiconductor device and its manufacturing method in accordance with thepresent invention can be adopted to other devices such as an organic ELdevice. Further, the semiconductor device of the present invention maybe generally used as a highly-functional integrated circuit.

As described above, the single-crystal silicon substrate of the presentinvention comprises an oxidized film, a gate pattern, and an impurityion implanted interface on a surface of the single-crystal siliconsubstrate, and the surface is planarized after forming the oxidizedfilm, the gate pattern, and the impurity ion implanted interface, and adense position of implanted hydrogen ions, to which a predeterminedconcentration of hydrogen ions is implanted for a predetermined depth.

According to this arrangement, the side of the single-crystal siliconsubstrate, where the oxidized film is formed, is bonded with a membersuch as the insulating substrate, and owing to the heat treatment, thesubstrates are bonded with siloxane bond so that the substrates becometightly bonded, and also, since the cleavage stripping at the denseposition is conducted by heating, it is possible to obtain a MOSsingle-crystal silicon thin-film transistor with ease, even if anadhesive is not used.

That is to say, the single-crystal silicon substrate of the presentinvention is arranged so that, on the surface thereof, the oxidizedfilm, gate pattern, and impurity ion implanted interface are formed asparts of the MOS single-crystal silicon thin-film transistor, and thedense position is provided at a predetermined depth from the surface ofthe substrate.

Further, the single-crystal silicon substrate of the present inventioncomprises: an impurity ion implanted/diffused area in which a PNPjunction structure or an NPN junction structure, to which impurity ionsare implanted, is provided near a surface of the single-crystal siliconsubstrate; and an oxidized film formed on the impurity ionimplanted/diffused area.

With this arrangement, it is possible to obtain a bipolar thin-filmtransistor made by a single-crystal silicon thin film which can beeasily formed on another insulating substrate.

Thus, for instance, on the insulating substrate on which anon-single-crystal (e.g. polycrystalline) silicon thin film is formed,the single-crystal silicon substrate of the present invention is bondedso that a bipolar single-crystal silicon thin-film transistor is formed,and hence it is possible to easily obtain a semiconductor device inwhich a transistor made from non-single-crystal silicon and a transistormade from a single-crystal silicon are formed on different areas of onesubstrate.

Further, according to the arrangement above, it is preferable that thesingle-crystal silicon substrate of the present invention furthercomprises a dense position of implanted hydrogen ions to which apredetermined concentration of hydrogen ions is implanted for apredetermined depth.

With this arrangement, a side of a single-crystal silicon substrate, theside to which an oxidized film is deposited, is bonded with a membersuch as an insulating substrate, and then the bonded substrates aresubjected to cleavage stripping, so that a bipolar single-crystalsilicon thin-film transistor can be easily obtained without using anadhesive.

That is to say, the single-crystal silicon substrate of the presentinvention is arranged such that an oxidized film and an impurity ionimplanted interface, which are for forming a bipolar single-crystalsilicon thin-film transistor, are formed thereon, and a dense positionof implanted hydrogen ions is provided at a predetermined depth from apart where the junction is formed.

Thus, the single-crystal silicon thin-film transistor is bonded with theinsulating substrate and then heating is carried out so that atemperature is increased to be not less than the temperature of hydrogendissociation from silicon, and hence the adhesive strength between thesingle-crystal silicon thin-film transistor and the insulating substrateis enhanced, and since the cleavage stripping is performed at the denseposition formed around the impurity ion implanted interface, it ispossible to easily form an SOI bipolar single-crystal silicon thin-filmtransistor, without using an adhesive.

Then the single-crystal silicon substrate of the present invention isbonded with the insulating substrate on which the non-single-crystal(e.g. polycrystalline) silicon thin film is formed, so that thesingle-crystal silicon thin-film transistor is formed. With thisarrangement, it is possible to easily obtain a semiconductor device inwhich a thin-film transistor made from non-single-crystal silicon and athin-film transistor made from single-crystal silicon are formed indifferent areas on one substrate.

Further, according to the arrangement above, the single-crystal siliconsubstrate of the present invention is preferably arranged such that athickness of the oxidized film is not less than 200 nm.

Basically, the thicker the oxidized film such as a SiO₂ film is, themore the degradation of the characteristics and the variation due to asurface charge, etc. are reduced. However, taking the efficiency (thetime required for oxidization) in the step of forming the SiO₂ film andthe unevenness into consideration, an appropriate thickness is about200-400 nm. The thickness is preferably not less than 400 nm when thereduction of the variation is emphasized. In the meantime, the thicknessis substantially within the range of 200-400 nm, more preferably 250-350nm when the elimination of the unevenness or the efficiency isemphasized. This is because the contamination of the interface betweenthe single-crystal silicon substrate and the insulating substrate suchas a glass substrate and the influence of a fixed electric charge causedby the distortion or incompleteness of the lattice are relieved.

Thus, according to the present invention, the variation of the thresholdis restrained in the case of a MOS transistor made from single-crystalsilicon and the variation of the characteristics and the ON-voltage arerestrained in the case of a bipolar TFT made from single-crystalsilicon, so that a single-crystal silicon substrate in which theefficiency of the step of forming a SiO₂ film and the balance of theunevenness are proper can be obtained.

Further, the SOI substrate of the present invention, in which asingle-crystal thin film is provided on an insulating substrate,comprises: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which thesingle-crystal silicon substrate is covered, the single-crystal siliconsubstrate being separated at the depth at which hydrogen ion isimplanted so that the single-crystal silicon thin film is formed, theinsulating substrate being a light-transmitting substrate, and thesingle-crystal silicon substrate being separated by means of heattreatment.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture transistors which can meet strict demands for thevariation and performance.

Also, since the insulating substrate is a light-transmitting substrate,the SOI substrate can be adopted as an active matrix substrate of adisplay device.

Also, since hydrogen ions which are much lighter than oxygen ions areimplanted, the implantation does not significantly change thecrystalline on the entire surface of the single-crystal siliconsubstrate, and hence the degradation of the crystalline of the silicondue to the implantation of hydrogen ions does not occur.

Also, by the heat treatment, the condition of the crystalline of thesingle-crystal silicon thin film is recovered to be the level before theimplantation of the hydrogen ions. The heat treatment is carried out ata temperature about, for instance, 600° C. This treatment does notdeteriorate the bonding characteristics at the bonded interface.

Further, the SOI substrate of the present invention, in which asingle-crystal silicon thin film is provided on an insulating substrate,comprising: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate at a dense position of implanted hydrogen ions by means ofheat treatment, and at the bonded interface, the insulating film isarranged to satisfy that a tan θ is not more than 0.06, where θ is theangle between (i) a maximum slope curve of micro-roughness, themicro-roughness being measured in a 1-5 μm square and not more than 5 nmin height, and (ii) an average surface plane.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture a transistor which can meet strict demands for thevariation and performance.

Note that, the tangent in the present case is an absolute value of thetangent. For this reason, in the arrangement above, the absolute valueof the tangent is not less than 0 and not more than 0.06. The foregoinginsulating film has micro-roughness on its surface, and the tangent ofthe maximum slope of these micro-roughness to the surface of theinsulating substrate is not more than 0.06. More specifically, forinstance, the tangent of the maximum slope of micro-roughness measuredin a 1-5 μm square on the surface of the insulating film to the surfaceof the insulating substrate is not more than 0.06, the micro-roughnessbeing not more than 5 nm in height.

By restraining the micro-roughness to be small as above, it is possibleto enhance the adhesive strength between the insulating film and thecovering film with which the single-crystal silicon substrate iscovered.

Further, the tangent is more preferably not more than 0.04. Thisarrangement makes it possible to further enhance the adhesive strengthbetween the insulating film and the covering film with which thesingle-crystal silicon substrate is covered.

Thus, it is possible to solve such a problem that the bondingcharacteristics between a light-transmitting substrate and asingle-crystal silicon substrate are degraded due to the micro-roughnesson the surface of the light-transmitting substrate.

Note that, in the SOI substrate, the condition of the surface of theinsulating film used for bonding the insulating substrate with thesingle-crystal silicon substrate can be evaluated by performing an AFMmethod with respect to, for instance, the micro-roughness of the surfacewhich is caused by the separation of the insulating substrate from thesingle-crystal silicon substrate.

Further, the SOI substrate of the present invention, in which asingle-crystal silicon thin film is provided on an insulating substrate,comprises: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate, and contact angles of a surface of the insulating film and asurface of the covering film with respect to water being not more than10°.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture a transistor which can meet strict demands for thevariation and performance.

Here, the insulating film is, for instance, an oxidized silicon filmwith which the insulating substrate is covered, and the covering filmis, for instance, an oxidized silicon film formed by oxidizing thesingle-crystal silicon substrate. The water may be pure water ordistilled water. Also, since the contact angle is always more than 0°(because complete wetting is indicated when the contact angle is 0°).the arrangement above is equivalent to state that the contact angle isnot less than 0° and not more than 10°.

The insulating film and the covering film have good water wettability,because the contact angle with respect to the water is not more than10°. Since surfaces having good water wettability are suitably bondedwith each other, even if, for instance, the insulating film and thecovering film are bonded with each other and then the single-crystalsilicon substrate is stripped and separated by heat treatment, thesingle-crystal silicon thin film bonded with the insulating substratedoes not peeled off. On this account, the present arrangement makes itpossible to provide a high-quality SOI substrate.

More specifically, it is possible to bond the insulating film with thecovering film, for instance, without using an adhesive. In this case,the condition, cleanliness, and degree of activity of the respectivesurfaces of the films are important factors. The bonding without usingan adhesive is realized thanks to contributions by van der Waals force,electric dipole, and hydrogen bond. The respective surfaces of thesubstrates are easily bonded with each other especially when both of thesurfaces are similarly arranged in terms of the balance of theabove-mentioned contributions. According to the foregoing arrangement,since the surfaces both having good water wettability are bonded witheach other, the surfaces are similarly arranged in terms of the balanceof the above-mentioned contributions so that the bonding characteristicsare good.

Although only the contact angles of the respective films with respect tothe water are described above, the contact angle with respect toethylene glycol or methylene iodide liquid may be measured.

Incidentally, the insulating film and the covering film may be washedusing a washing liquid made by diluting ammonia and hydrogen peroxide byde-ionized water. By performing the washing in this manner, it ispossible to remove particles from the respective surfaces of theinsulating film and the covering film before the bonding, and henceclean surfaces can be certainly obtained. With this arrangement, it ispossible to restrain the contact angle with respect to the water on thesurface to be not more than 10°, with more certainty.

Further, the SOI substrate of the present invention, in which asingle-crystal silicon thin film is provided on an insulating substrate,comprises: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate, and the insulating film being an oxidized silicon film formedby a plasma chemical vapor deposition method using a gas mixture of aTEOS gas and an oxygen gas.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture a transistor which can meet strict demands for thevariation and performance.

Here, the TEOS gas is a Tetra Ethyl Ortho Silicate gas.

When the formation of the film is performed by a plasma chemical vapordeposition method using a gas in which a TEOS gas and an oxygen gas asabove, the obtained insulating film can be easily bonded with thecovering film. In contrast, the insulating film formed by a sputteringmethod cannot easily be bonded with the covering film.

Further, the SOI substrate of the present invention, in which asingle-crystal silicon thin film is provided on an insulating substrate,comprises: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate, and at the bonded interface, the insulating film which ismade of oxidized silicon and 5-300 nm thick being bonded.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture a transistor which can meet strict demands for thevariation and performance.

The insulating film is an oxidized silicon film whose thickness iswithin the range of 5-300 nm. This insulating film is bonded so that thebonded interface is formed. According to this arrangement, since theoxidized silicon film is thick, the influence of a fixed electric chargeon the surface of the light-transmitting substrate is restrained so thatthe characteristics of the transistor formed on the single-crystalsilicon thin film of the SOI substrate can be improved. Morespecifically, even if a fixed electric charge is generated on theinterface between the silicon and insulating substrate, thesingle-crystal silicon thin film is not influenced by the fixed electriccharge so that the threshold voltage of the thin-film transistor can besuitably controlled and hence a desired threshold voltage can beobtained.

The thickness of the insulating film is more preferably within the rangeof 40-300 nm. With this arrangement, it is possible to certainlyrestrain the influence of the fixed electric charge on the surface ofthe light-transmitting substrate and improve the characteristics of thetransistor.

Further, the SOI substrate of the present invention, in which asingle-crystal silicon thin film is provided on an insulating substrate,comprises: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate, and an adhesive strength at the bonded interface being notless than 0.6 N/m.

In this SOI substrate, the single-crystal silicon substrate is bondedwith the insulating substrate, and this single-crystal silicon substrateis separated and stripped at the implanted interface so that thesingle-crystal silicon thin film is obtained. With this arrangement, itis possible to form a single-crystal silicon thin film in which thecrystal axis in the silicon film are uniform. Further, theabove-described arrangement makes it possible to obtain transistorswhich are uniform and high-performance. That is to say, the variation ofthe characteristics (threshold voltage and mobility) between thetransistors is restrained and the improvement of the performance, suchas the improvement of the mobility, is realized so that it is possibleto manufacture a transistor which can meet strict demands for thevariation and performance.

Here, the adhesive strength is a strength per a unit length, which isrequired for peeling a thin film off from an object, against its surfacetractive force.

Improving the adhesive strength as above makes it possible to preventthe peeling-off of the thin film. In a conventional arrangement, theadhesive strength at a bonded interface is about 0.2 N/m. In contrast,according to the present invention, the adhesive strength is not lessthan 0.6 N/m and hence the peeling-off can be prevented.

Note that, in the present arrangement, the evaluation of the adhesivestrength is carried out before improving the adhesive strength bymethods such as heat treatment. Thus, by conducting heat treatment afterthe evaluation, it is possible to improve the adhesive strength forabout 10-1000 times.

Further, according to the arrangement above, the SOI substrate of thepresent invention may be arranged in such a manner that a single-crystalthin-film device is formed on the single-crystal silicon substrate, andthe single-crystal thin-film contains the single-crystal thin-filmdevice being formed by separating the single-crystal silicon substrate.

Also by this arrangement, it is possible to realize an SOI substrate onwhich the single-crystal silicon thin film is provided with thesingle-crystal thin-film device.

Further, the SOI substrate of the present invention may comprise: asingle-crystal silicon thin-film device manufactured from thesingle-crystal silicon thin film; and a non-single-crystal siliconthin-film device which is manufactured from a non-single-crystal siliconthin film, and the non-single-crystal silicon thin film is provided inan area on the insulating substrate, the area being different from anarea where the single-crystal silicon thin film is provided.

Also by this arrangement, it is possible to realize the SOI substrate onwhich the single-crystal silicon thin film is provided with thesingle-crystal thin-film device and the non-single-crystal silicon thinfilm provided with the non-single-crystal thin-film device.

Further, the semiconductor device of the present invention comprises: anon-single-crystal silicon thin-film device manufactured from anon-single-crystal silicon thin film and a single-crystal siliconthin-film device manufactured from a single-crystal silicon thin film,wherein the non-single-crystal silicon thin-film device and thesingle-crystal silicon thin-film device are provided in different areasof an insulating substrate.

According to the above, for instance, a single-crystal silicon thin-filmdevice such as a single-crystal silicon thin-film transistor is adoptedto devices which have to be highly functional, such as a timingcontroller, while a non-single-crystal silicon thin-film device such asa non-single-crystal silicon thin-film transistor is adopted to otherdevices. With this arrangement, it is possible to obtain a semiconductordevice in which high-performance and highly-functional circuit systemsare integrated.

That is to say, by adopting a single-crystal silicon thin-film device,devices such as a fast and low-power-consumption logic circuit andtiming generator and a fast DAC (current buffer) from which variationhas to be eliminated can be formed. Meanwhile, although the performanceand characteristics of a non-single-crystal silicon (e.g.polycrystalline silicon) thin-film device are inferior to theperformance and characteristics of the single-crystal silicon thin-filmdevice, it is possible to form a large and cheap semiconductor device byadopting the non-single-crystal silicon thin-film device.

Thus, according to the present invention, it is possible to form asemiconductor device having the advantages of the both silicon thin-filmdevices, on a single substrate.

On this account, high-performance and highly-functional circuit systemswhich can be realized only by adopting single-crystal silicon can beintegrated on a single substrate. For instance, a semiconductor devicefor a display device in which high-performance systems are integrated,such as a liquid crystal panel and an organic EL panel, can bemanufactured with significantly lower costs, compared to a case when alldevices are made by single-crystal silicon.

The shape of the single-crystal silicon substrate by which thesingle-crystal silicon thin film of the semiconductor device of thepresent invention is formed has to be a disk which is sized 6, 8, or 12inch in diameter. Note that, the disk which is sized 6, 8, or 12 inch indiameter is a typical wafer for manufacturing LSI. However, since thenon-single-crystal silicon thin-film device and the single-crystalsilicon thin-film device coexist on the insulating substrate of thesemiconductor device of the present invention, it is possible tomanufacture, for instance, a large semiconductor device which can beadopted to a large liquid crystal display panel and a large organic ELpanel.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that thesingle-crystal silicon thin-film device is bonded with the insulatingsubstrate via an inorganic insulating film interposed therebetween.

With this arrangement, it is possible to form a device such as asingle-crystal silicon thin-film transistor on the insulating substratewithout using an adhesive, and hence the contamination of thesingle-crystal silicon can be prevented. Further, after carrying out thebonding, the formation of a metal wiring and inorganic insulating filmand etching can be easily performed. Since the metal wiring, etc. areformed simultaneously with a TFT process on a large substrate, it ispossible to manufacture the device with low costs.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that eachof the non-single-crystal silicon thin-film device and thesingle-crystal silicon thin-film device is either a MOS thin-filmtransistor or a MIS thin-film transistor.

With this arrangement, when, for instance, a CMOS structure is adopted,it is possible to manufacture a semiconductor device in which the powerconsumption is reduced, an output voltage can swing up to thepower-supply voltage, and the logic of low power consumption is suitablyadopted.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, inthe MOS thin-film transistor, a gate, a gate insulating film, and asilicon are formed on the insulating substrate in this order.

With this arrangement, the MOS single-crystal silicon thin-filmtransistor is formed so that the gate of the transistor is provided onthe side of the insulating substrate, and hence it is possible to obtaina semiconductor device in which an upended MOS single-crystal siliconthin-film transistor is provided on an insulating substrate. Thus, aself-aligning process in which the source and drain of thesingle-crystal silicon substrate are formed by masking by the gate canbe adopted, the influence of a fixed electric charge on the surface ofthe glass substrate can be restrained, the influence of a fixed electriccharge which tends to occur at the bonded interface between thesingle-crystal silicon and the glass substrate can be restrained thanksto the shielding effect of the gate, and an established process ofcarrying out the impurity ion implantation to the source and drain ofthe single-crystal silicon can be adopted using the gate as a mask. Forthese reasons, the production yields can be improved.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, athickness of a silicon thin film of the MOS thin-film transistor isabout not more than 600 nm.

According to this arrangement, in the semiconductor device, a thicknessd of the single-crystal silicon thin film is small in consideration ofthe margin of the variation with respect to the maximum depletion lengthWn which is determined by an impurity concentration Ni, and hence thethickness d is about not more than 600 nm, even if the impurityconcentration is 10¹⁵ cm⁻³ which is the lower practical limit.

In this case, Wm=[4ε_(s)kTln(Ni/ni)q²Ni]^(1/2), where ni is an intrinsiccarrier concentration, k is a Boltzmann constant, T is an absolutetemperature, ε_(s) is a permittivity of silicon, q is an electriccharge, and Ni is an impurity concentration.

According to the arrangement above, since the thickness of thesingle-crystal silicon thin film is about not more than 600 nm, anS-value (subthreshold coefficient) of the semiconductor device can beset to be small and the OFF-current can be reduced. Thus, the MOSsingle-crystal silicon thin-film transistor can exercise its fullpotential.

More preferably, the thickness of the single-crystal silicon thin filmof the MOS thin-film transistor is about not more than 100 nm.

According to this arrangement, the S-value (subthreshold coefficient) ofthe semiconductor device can be further set to be small and theOFF-current can be reduced. Thus, the MOS single-crystal siliconthin-film transistor can exercise its full potential.

In particular, to restrain the degradation of the TFT characteristicsdue to the quantum effect caused in a short-channel TFT in which thegate length is in the range of 0.1-0.2 μm or less, the thickness ispreferably about not more than 20 nm. Provided that the gate length isabout not more than 200 nm, when the single-crystal silicon is thickerthan 20 nm, the mobility increases but the variation of the thresholdvalue also increases. Since the restraint of the variation of thethreshold value is more important for the device, the thickness above isgenerally practical.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, ametal pattern of the MOS single-crystal silicon thin-film transistor isformed under a wiring rule which is more relaxed than a wiring rule of agate pattern of the MOS single-crystal silicon thin-film transistor.Also, the wiring rule of the metal pattern of the MOS single-crystalsilicon thin-film transistor is preferably as strict as or more relaxedthan the wiring rule of a metal pattern on a large substrate. Further,the wiring rule of the metal pattern of the MOS single-crystal siliconthin-film transistor is preferably either (i) as strict as the wiringrule of the metal pattern equivalent to the gate of the TFT, or (ii) asstrict as or more relaxed than the wiring rule of the metal pattern on alarge substrate constituted by a plurality of different wiring layers.

With this arrangement, at least a part of the metal wiring pattern ofthe semiconductor device on which the MOS single-crystal siliconthin-film transistor is provided can correspond to micro-fabricationequivalent to the micro-fabrication for the gate and can be processedsimultaneously with the metal wiring pattern on the large substrate, andhence the costs can be reduced and the processing power can be improved.Further, since the connection to other circuit blocks and a TFT arraybecomes easy, the drop of the production yields due to alignment failurecan be restrained.

Note that, when a wiring rule is relaxed, a design rule for forming awiring is not strict and a permissible range on the occasion of formingthe wiring is broad.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin-film device is either a MOSnon-single-crystal silicon thin-film transistor or a MISnon-single-crystal silicon thin-film transistor, and the single-crystalsilicon thin-film device is a bipolar single-crystal silicon thin-filmtransistor.

According to this arrangement, in addition to the MOS or MISnon-single-crystal silicon thin-film transistor, the bipolarsingle-crystal silicon thin-film transistor is formed so that asemiconductor device having various functions can be obtained.

That is to say, since the bipolar single-crystal silicon thin-filmtransistor is formed in addition to the MOS or MIS non-single-crystalsilicon thin-film transistor, it is possible to obtain a semiconductordevice having advantages of a bipolar thin-film transistor, that is tosay, the linear signal processing can be performed, the structure issimple because of the omission of the gate so that the production yieldsare good, the linearity in a saturation area is good, and suitabilityfor an analog amplifier, current buffer, and power supply amplifier isobtained.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin-film device is either a MOSnon-single-crystal silicon thin-film transistor or a MISnon-single-crystal silicon thin-film transistor, and the single-crystalsilicon thin-film device includes at least either one of a MOSsingle-crystal silicon thin-film transistor and a bipolar single-crystalsilicon thin-film transistor.

With this arrangement, it is possible to form a semiconductor devicehaving the characteristics of three transistors, namely the MOS or MISnon-single-crystal silicon thin-film transistor, the single-crystalsilicon thin-film transistor, and the bipolar single-crystal siliconthin-film transistor, on a single substrate.

Thus, it is possible to obtain a semiconductor device which has higherperformance and is more functional.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin-film device is either a MOSnon-single-crystal silicon thin-film transistor or a MISnon-single-crystal silicon thin-film transistor, and the single-crystalsilicon thin-film device includes a MOS single-crystal silicon thin-filmtransistor, and an image sensor including a Schottky or PN-junctiondiode or a CCD image sensor.

With this arrangement, differently-arranged or differently-structuredthin-film devices provided can be integrated in different areas, andhence CMOS devices such as an image sensor and devices having structuresdifferent from those of the CMOS devices can be integrated with ease,even if the coexistence of these devices has conventionally beenextremely difficult, so that highly-functional devices which have notbeen able to be manufactured can be created.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, athickness of a single-crystal silicon thin-film of the MOSsingle-crystal silicon thin-film transistor is thinner than a thicknessof a single-crystal silicon thin film of the bipolar single-crystalsilicon thin-film transistor.

It has been well-known that, in the case of the MOS thin-filmtransistor, generally the thinner the film is, the better thecharacteristics are, and in the case of the bipolar thin-filmtransistor, good characteristics (i.e. variation is small andON-resistance is low) can be obtained when the film is relatively thick.

Thus, according to the present invention, the thicknesses of the MOSsilicon thin film and the bipolar silicon thin film are compared witheach other so as to be determined, and hence a semiconductor devicewhich can utilize the characteristics of the both MOS and bipolartransistors can be obtained.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thebipolar single-crystal silicon thin-film transistor has such a structurethat a base area, a collector area, and an emitter area are formed andprovided in one plane.

According to this arrangement, unlike the MOS thin-film transistor, thebipolar transistor is a planarized, i.e. laterally-structured transistorwhich has no gates, and hence a silicon substrate whose surface iscompletely flat can be formed only by forming an oxidized film on thesurface of silicon, performing implantation of P-impurities andN-impurities to a predetermined pattern (area), and performingactivation annealing. Thus, it is possible to easily bond thesingle-crystal silicon substrate with the insulating substrate, withoutcarrying out a planarizing process by CMP.

For this reason, compared with a conventional MOS transistor or abipolar transistor in which the bonding is performed in the directionorthogonal to its surface, the manufacturing process can be simplified.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, ametal wiring and a contact pattern of the bipolar single-crystal siliconthin-film transistor include respective parts each being formed inaccordance with a wiring rule which is more relaxed than a wiring ruleof a base pattern of the bipolar single-crystal silicon thin-filmtransistor. Further, it is more preferable that the metal pattern andthe contact pattern of the bipolar single-crystal silicon thin-filmtransistor are formed in accordance with a wiring rule which is asstrict as or more relaxed than the design rule of a metal wiring patternon a large substrate.

With this arrangement, at least a part of the metal wiring can beprocessed simultaneously with the metal wiring on the large substrate,and hence the costs can be reduced and the processing power can beimproved. Further, since a semiconductor device on which the bipolarsingle-crystal silicon thin-film transistor is formed can be easilyconnected to members such as other circuit blocks or a TFT array, it ispossible to prevent the degradation of the production yields due to thealignment failure.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, athickness of the single-crystal silicon thin film of the bipolarsingle-crystal silicon thin-film transistor is about not more than 800nm.

With this arrangement, it is possible to manufacture a bipolarsingle-crystal silicon thin-film transistor in which the variation ofthe characteristics is small and the ON-resistance is low.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin film is either a polycrystalline siliconthin film or a continuous grain silicon thin film, and a MOS thin-filmtransistor manufactured from the non-single-crystal silicon thin filmincludes a non-single-crystal silicon, a gate insulating film, and agate on the insulating substrate in this order.

According to this arrangement, by forming a MOS thin-film transistor inwhich a gate is provided at the furthest from the insulating substrate,a self-aligning process using a conventional gate as a mask can beadopted, and hence a polycrystalline silicon thin film or a continuousgrain silicon thin film can be easily manufactured and the productionyields can be improved.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin film is either one of a polycrystallinesilicon thin film or a continuous grain silicon thin film, and a MOSthin-film transistor manufactured from the non-single-crystal siliconthin film includes a gate, a gate insulating film, and anon-single-crystal silicon on the insulating substrate in this order.

With this arrangement, the MOS non-single-crystal silicon thin-filmtransistor is provided in an upend manner so that the influence of afixed electric charge around the surface of the glass substrate can beavoided, and the characteristics can be stabilized. Further, the dopingprofile of the channel section can be arranged more freely, sincemicro-fabrication and doping can be performed in the manufacturingprocess of VLSI. Thus, taking countermeasures against the hot electrondegradation becomes easy. Further, a thin, high-qualitythermally-oxidized SiO₂ can be adopted, it is possible to obtain a gateoxidized film which is thinner and has better quality than an oxidizedfilm formed at low temperatures by methods such as CVD, so that a TFTwhich excels in short-channel characteristics can be obtained. On thisaccount, it is possible to increase the number of variations ofarrangements for obtaining effects similar to the above.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin film is either one of a polycrystallinesilicon thin film or a continuous grain silicon thin film, and a MOSthin-film transistor manufactured from the non-single-crystal siliconthin film includes a gate, a gate insulating film, and anon-single-crystal silicon on the insulating substrate in this order.

With this arrangement, by manufacturing a bottom-gate MOS or MISthin-film transistor in which a gate is provided so as to be closest tothe insulating substrate, it is possible to adopt conventionally knownmanufacturing processes, and hence the process of manufacturing anamorphous silicon thin film can be simplified, the costs for the processis reduced, and the productivity is improved. Also, in an active matrixLCD, the shading property regarding a backlight is improved so that aliquid crystal display device which can perform high-luminancedisplaying can be formed.

Moreover, since the amorphous silicon has low-OFF-currentcharacteristics, it is possible to obtain a semiconductor device whichcan be adopted to a low-power-consumption LCD.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, thenon-single-crystal silicon thin film is an amorphous silicon thin film,and a MOS thin-film transistor or a MIS thin-film transistor, which ismanufactured from the non-single-crystal silicon thin film, includes anon-single-crystal silicon, a gate insulating film, and a gate on theinsulating substrate in this order.

With this arrangement, even if a MOS or MIS non-single-crystal siliconthin-film transistor is arranged in an upend manner with respect to asubstrate, it is possible to increase the number of variations ofarrangements for obtaining effects similar to the above, so that thedegree of freedom for process designing increases.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, adifference of linear expansion between a single-crystal siliconconstituting the single-crystal silicon thin-film device and theinsulating substrate is about not more than 250 ppm, within atemperature range from a substantially room temperature and 600° C.

With this arrangement, the difference of linear expansion between theinsulating substrate and the single-crystal silicon thin film on theoccasion of great temperature rise is reduced. Thus, in the step offorming the single-crystal silicon thin film on the insulatingsubstrate, it is possible to certainly prevent (i) the crack of theinsulating substrate caused by the difference of linear expansioncoefficients, when cleavage stripping occurs at the dense position ofimplanted hydrogen ions in silicon to which hydrogen ions are implanted,(ii) the peeling-off from the bonded interface, and (iii) the crystaldefect, thereby improving the heat adhesive strength.

Note that, the linear expansion is a standard of the variation of alength due to temperature variation.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, theinsulating substrate is a high strain point glass including analkaline-earth alumino-borosilicate glass, and a SiO2 film is formed atleast in an area on a surface of the insulating substrate, where thesingle-crystal silicon thin-film device is to be formed.

With this arrangement, since it is unnecessary to use a crystallineglass whose composition is modified in order to correspond to thebonding with the single-crystal silicon substrate, it is possible tomake an insulating substrate from a high strain point glass typicallyused for an active matrix liquid crystal display panel, and hence asemiconductor device can be manufactured at low costs.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, theinsulating substrate is manufactured from at least one glass selectedfrom the group consisting of a barium-borosilicate glass, abarium-alumino-borosilicate glass, an alkaline-earthalumino-borosilicate glass, a borosilicate glass, an alkaline-earthzinc-lead-alumino-borosilicate glass, and an alkaline-earthzinc-alumino-borosilicate glass.

According to this arrangement, since the insulating substrate is madefrom the above-described high strain point glass typically used for anactive matrix liquid crystal display panel, it is possible tomanufacture a semiconductor device suitable for an active matrixsubstrate, at low costs.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, amargin of alignment of at least a part of a pattern on thesingle-crystal silicon is fine so as to be smaller than a margin ofalignment of patterns on any one of an entire surface of a mother board,a display area, and an entirety of the non-single-crystal siliconthin-film device and the single-crystal silicon thin-film device.

With this arrangement, when, for instance, a metal wiring pattern whichis equivalent to the pattern in the non-single-crystal silicon area isformed, it is possible to cause a part of the pattern to be aligned witha high-definition pattern in an area of the single-crystal silicon,using a high-definition exposure system.

Thus, with good production yields, it is possible to easily andefficiently connect a single-crystal silicon area with a high-definitionpattern with a non-single-crystal area with a low-definition pattern,using a metal wiring pattern, etc.

Further, according to the arrangement above, the semiconductor device ofthe present invention is preferably arranged in such a manner that, analigning mark formed on the single-crystal silicon is detected usingvisible light or light whose wavelength is shorter than the visiblelight, through a transparent substrate, and has a form which allows thealigning mark to be aligned with an aligning mark formed on thetransparent substrate.

With this arrangement, since the aligning mark can be detected throughthe glass substrate, the optical resolution can be improved so that thealignment can be carried out more precisely than a conventionalarrangement.

Further, to achieve the foregoing objectives, the semiconductor deviceof the present invention includes any one of the above-described SOIsubstrates each including a semiconductor device structure formedthereon. Here, the above-mentioned SOI substrates are semiconductordevices each including a semiconductor device structure formed thereon.

Further, to achieve the foregoing objectives, the display device of thepresent invention includes any one of the above-described semiconductordevice, uses the semiconductor device as an active matrix substrate of adisplay panel.

Since, in the SOI substrate, the insulating substrate is alight-transmitting substrate, forming a semiconductor device structureon this insulating substrate allows the SOI substrate to be suitablyused as an active matrix substrate for a display panel.

Moreover, since high-performance transistors with no variations can beobtained by adopting the foregoing SOI substrate, it is possible toprovide a high-performance display device using this transistor.

In this manner, the characteristics of the transistor can be caused tobe uniform, stabilized, and high-performance by adopting thesingle-crystal silicon, and hence it is possible to manufacture, forinstance, a high-performance MOS field effect transistor device. On thisaccount, using this transistor device, it is possible to manufacture ahigh-performance TFT-LCD display device and TFT-OLEDL display device.

Note that, the semiconductor device structure is, for instance, astructure as a switching device for displaying. Also, it is possible tomanufacture an image processor by forming a semiconductor devicestructure on an SOI substrate.

To put it another way, for instance, the display device includes aswitching element for displaying and an image processor which aremanufactured using an insulating substrate partly having an SOIstructure thereon, the insulating substrate being manufactured in such amanner that a light-transmitting substrate whose surface is covered withan oxidized silicon film is bonded with a single-crystal siliconsubstrate whose surface is oxidized, and then the single-crystal siliconsubstrate is separated at a predetermined interface by heat treatment.

Further, a method of manufacturing the semiconductor device of thepresent invention, in which a single-crystal silicon thin-film devicemanufactured from a single-crystal silicon thin film and anon-single-crystal silicon thin film are formed on an insulatingsubstrate, is arranged in such a manner that, after a circuit includingthe single-crystal silicon thin-film device is formed on the insulatingsubstrate, the non-single-crystal silicon thin film is formed.

According to this method, a single-crystal silicon thin-film device isformed on a flat insulating substrate, and then a non-single-crystalsilicon thin film is formed. Thus, the defection due to alignmentfailure can be restrained so that a semiconductor device can bemanufactured with good productive yields.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, on the single-crystal silicon thin-film device, aprotective interlayer insulating film, a contact hole, and a metalwiring are formed.

According to this method, since the single-crystal silicon thin-filmdevice which is formed prior to the formation of the non-single-crystalsilicon thin film has a metal wiring, micro-fabrication can be carriedout so that the degree of density of circuit integration on thesingle-crystal silicon thin film can be greatly increased. Moreover, byan identical process, a metal wiring is also formed on thenon-single-crystal silicon thin film which is formed after the formationof the single-crystal silicon thin-film device on the glass substrate,so that a semiconductor device with a double-metal-wiring arrangementcan be efficiently manufactured by a simple process.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, after the single-crystal silicon thin-film deviceis formed, an interlayer insulating film is formed, and then thenon-single-crystal silicon thin film is formed.

According to this method, since the interlayer insulating film is formedbetween the single-crystal silicon thin-film device and thenon-single-crystal silicon thin film, it is possible to certainlyprevent the contamination of the single-crystal silicon of thesingle-crystal silicon thin film.

A method of manufacturing the semiconductor device of the presentinvention, in which a single-crystal silicon thin-film devicemanufactured from a single-crystal silicon thin film and anon-single-crystal silicon thin film are formed on an insulatingsubstrate, is arranged such that, after the non-single-crystal siliconthin film is formed on the insulating substrate, the single-crystalsilicon thin-film device is formed.

According to this method, since the non-single-crystal silicon thin filmis formed prior to the formation of the single-crystal silicon thin-filmdevice, the contamination and damage of the single-crystal silicon thinfilm are prevented, compared to a case that the non-single-crystalsilicon thin film is formed after the formation of the single-crystalsilicon thin-film device.

In a method of manufacturing a semiconductor device in which asingle-crystal silicon thin-film device and a non-single-crystal siliconthin-film are formed on an insulating substrate, when the single-crystalsilicon thin-film device is formed after the formation of thenon-single-crystal silicon thin film on the insulating substrate, thesurface of the insulating substrate, from which the non-single-crystalsilicon is removed and to which the single-crystal silicon is to bebonded, is roughened up so that the micro-roughness increases and hencethe adhesive strength deteriorates.

To solve this problem, in the method of manufacturing the semiconductordevice of the present invention, at least the area to which thesingle-crystal silicon is to be bonded is planarized in advance by GCIB(Gas Cluster Ion Beam) using low-energy (about 3 Kev) halide (such asCF₄). When, further on this area, a SiO₂ film which is about 10 nm thickis formed by PECVD using TEOS or TMCTS (Tetramethylcyclotetrasiloxane),the bonding characteristics are further improved.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, the single-crystal silicon thin-film device is aMOS single-crystal silicon thin-film transistor.

With this arrangement, for instance, when, for instance, a CMOSstructure is adopted, it is possible to manufacture a semiconductordevice in which the power consumption is reduced, an output voltage canswing up to the power-supply voltage, and the logic of low powerconsumption is adopted.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, the single-crystal silicon thin-film device is abipolar single-crystal silicon thin-film transistor.

With this arrangement, forming the bipolar transistor on the insulatingsubstrate makes it possible to cause the arrangement of thesingle-crystal silicon thin film to be simpler than the arrangement inthe case of a MOS transistor, and this enables the single-crystalsilicon thin film to be bonded with the insulating film, without beingsubjected to planarization.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, with respect to a single-crystal siliconsubstrate for manufacturing the single-crystal silicon thin-film device,a predetermined concentration of hydrogen ions is implanted for apredetermined depth.

With this arrangement, it is possible to easily form the single-crystalsilicon thin-film device on the insulating substrate, without using anadhesive.

That is to say, when the single-crystal silicon thin-film device isformed on the insulating substrate, the dense position to which thehydrogen ions are implanted is formed and hence the adhesive strengthwith respect to the insulating substrate can be increased by increasingthe temperature to be not less than the temperature of hydrogendissociation from silicon. Then, by performing cleavage stripping at thedense position, it is possible to easily manufacture the bipolarsingle-crystal silicon thin-film transistor.

Note that, the above-mentioned predetermined depth is determined inaccordance with a desired thickness of the single-crystal silicon thinfilm to be formed.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, an energy for implanting the hydrogen ions isarranged so that an energy after subtracting an energy corresponding toa projection range of the hydrogen ions in a gate electrode material fora gate electrode thickness from an incident energy of the hydrogen ionsis no more than an energy corresponding to a projection range of theheaviest ions of gate constituent materials for a gate oxide thickness.

With this arrangement, for instance, it is possible to prevent theoccurrence of the following problem: In the MOS single-crystal siliconthin-film transistor, the hydrogen ions applied to the single-crystalsilicon substrate collide with the materials of gate electrodes andatoms constituting the materials of the metal wiring, so that the atomsconstituting the materials of the gate electrodes, which are knocked ondue to the collision, pass through the oxidized film, and consequentlyreach the single-crystal silicon and contaminate the same.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, a thickness of the single-crystal siliconsubstrate including the dense position is about not more than 100 μm.

With this arrangement, it is possible to cause the thickness of thesingle-crystal silicon layer to be about 1/10 of the substrate, andsince the flexural rigidity of the silicon substrate reduces, thesurface of the substrate becomes able to deform in accordance withmicro-roughness produced due to the roughness of the surface facing theglass substrate and particles on the surface, even if the bonding energyis identical, and hence the substrate is hardly influenced by themicro-roughness.

Thus, when the thickness is set as above, it is possible tosignificantly decrease the occurrence of alignment failure due to theroughness of the surface facing the glass substrate and the particles onthe surface, without greatly undermining the handiness of a small andthin silicon substrate which has been separated.

Incidentally, the above-mentioned thickness is preferably about not morethan 70 μm, and more preferably not more than 50 μm.

Further, according to the arrangement above, the method of manufacturingthe semiconductor device of the present invention is preferably arrangedin such a manner that, after the non-single-crystal silicon thin film isformed on the insulating substrate, at least a surface area from whichthe single-crystal silicon is removed and to which a single-crystalsilicon is to be bonded is planarized in advance by performing a GCIB(Gas Cluster Ion Beam) using halide in approximately 3 keV.

With this arrangement, the surface of silicon or SiO₂ is lightly etchedwhen low-energy (about 3 kev) GCIB of oxygen or halide is appliedthereto, so that the micro-roughness on the surface is reduced.

For this reason, the success rate of the bonding is significantlyimproved, compared to the bonding of a conventional silicon substrate.

To achieve the foregoing objectives, a method of manufacturing thesemiconductor device of the present invention, comprising the step of:(a) bonding an insulating film formed on an insulating substrate with acovering film with which a single-crystal silicon substrate is covered,is characterized by further comprising the step of: (b) before the step(a), regulating a tangent of a maximum slope of micro-roughness on asurface of the insulating film to a surface plane of the insulatingsubstrate, measured in a 1-5 μm square, is not more than 0.06, themicro-roughness being not more than 5 nm in height.

The SOI substrate is manufactured in such a manner that, after thebonding step, the single-crystal silicon substrate is separated andstripped at the dense position and thus the single-crystal silicon thinfilm is formed. That is to say, the above-described manufacturing methodis also a method of manufacturing an SOI substrate. That is to say,according to the manufacturing method, a semiconductor device ismanufactured either by forming a semiconductor device structure on asingle-crystal silicon thin film on the SOI substrate, or manufacturinga single-crystal silicon thin film from a single-crystal siliconsubstrate in which a semiconductor device structure is formed.

According to the manufacturing method, after the micro-roughness on thesurface of the insulating film is arranged so that the tangent of themaximum slope of micro-roughness on a surface of the insulating film toa surface plane of the insulating substrate, measured in a 1-5 μmsquare, is not more than 0.06, the insulating film is bonded with thecovering film with which the single-crystal silicon substrate iscovered. With this arrangement, the bonding characteristics are good sothat the adhesive strength is improved. Thus, the peeling of the filmdoes not occur when the single-crystal silicon substrate is separatedand stripped in order to form the single-crystal silicon thin film,after the bonding step.

In contrast, when the above-mentioned tangent is not less than 0.06, theadhesive strength at the bonded interface between the films is not morethan 0.2 N/m. In this case, the peeling of a part of the film isobserved after the stripping, separation, and annealing are performed.

Incidentally, in the regulating step, it is preferable to, for instance,appropriately set the thickness of the insulating film on the insulatingsubstrate and the condition of the formation of the film. When thesefactors are properly set, it is possible to certainly cause the tangentof the insulating film to the surface of the insulating substrate to benot more than 0.06. Note that, the insulating film is preferably not toothick. For instance, when the thickness of an oxidized silicon film asan insulating film is not less than 500 nm, it is preferable that theoxidized silicon film is polished after the formation thereof. Thethickness of the oxidized film is, for instance, preferably about 100nm.

Moreover, the tangent of the insulating film to the surface of theinsulating substrate is preferably not more than 0.04. This arrangementmakes it possible to prevent the peeling of the film with morecertainty.

Further, in the arrangement above, it is preferable that a step ofarranging the contact angles of the insulating film and the coveringfilm with respect to water is not more than 10° is included.

With this arrangement, the bonding characteristics between theinsulating film and the covering film is improved and the adhesivestrength is certainly enhanced, so that a method of manufacturing an SOIsubstrate in which the film peeling is further restrained can berealized.

The method of manufacturing the SOI substrate can be seen as a method ofmanufacturing the SOI substrate, including such a step that atemperature of the dense position of implanted hydrogen ions of thesingle-crystal silicon substrate is raised to be not less than thetemperature of hydrogen dissociation from silicon, by applying lightincluding laser light, and the single-crystal silicon substrate isseparated along the dense position.

According to this arrangement, since the temperature of the denseposition of the single-crystal silicon substrate is increased byapplying light including laser light, only the temperature around thedense position can be increased so that the destruction of thesingle-crystal silicon can be restrained.

Further, the method of manufacturing the SOI substrate can be seen as amethod of manufacturing the SOI substrate, which includes a step ofseparating the single-crystal silicon substrate along the denseposition, by performing lamp annealing in which the maximum temperatureis about not less than 850° C.

After the above-described arrangement, lamp annealing which is rapidthermal annealing (RTA) in which the maximum temperature is about notless than 850° C. is carried out and the single-crystal siliconsubstrate is exfoliated at the depth at which hydrogen ions areimplanted. With this arrangement, the bonding strength is furtherenhanced, and since the damage due to the hydrogen ion implantation onthe peeling interface and inside the single-crystal silicon thin film,the characteristics of the transistor are improved.

Incidentally, the higher the maximum temperature of the lamp annealingis, the more the characteristics of the transistor are improved.However, the higher the maximum temperature of the lamp annealing is,the more the warpage, expansion and contraction of the insulatingsubstrate become serious. Thus, when, for instance, the size of thesubstrate is about 300 mm per side, the annealing is carried out forabout 5 minutes at a temperature about 700° C.

Further, the method of manufacturing the SOI substrate can be seen as amethod of manufacturing the SOI substrate arranged such that byimplanting hydrogen ions which are much lighter than oxygen ions, thecrystalline on the entire surface of the single-crystal siliconsubstrate is not significantly changed even after the implantation.

According to the arrangement above, by performing heat treatment at atemperature about 600° C. in the TFT manufacturing step after thestripping, the condition of the crystalline of the single-crystalsilicon thin film is recovered to be the level before the implantationof the hydrogen ions. Unlike the case of implanting oxygen ions, thistreatment does not cause the degradation of the crystalline of thesilicon.

The invention being thus described, it will be obvious that the same waymay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A single-crystal silicon substrate, comprising: an oxidized film, agate pattern, and an impurity ion implanted interface on a surface ofthe single-crystal silicon substrate, and the surface is planarizedafter forming the oxidized film, the gate pattern, and the impurity ionimplanted interface, and a dense position of implanted hydrogen ions, towhich a predetermined concentration of hydrogen ions is implanted for apredetermined depth.
 2. A single-crystal silicon substrate, comprising:an impurity ion implanted/diffused area in which a PNP junctionstructure or an NPN junction structure, to which impurity ions areimplanted, is provided near a surface of the single-crystal siliconsubstrate; and an oxidized film formed on the impurity ionimplanted/diffused area.
 3. The single-crystal silicon substrate asdefined in claim 2, further comprising a dense position of implantedhydrogen ions, to which a predetermined concentration of hydrogen ionsis implanted for a predetermined depth.
 4. The single-crystal siliconsubstrate as defined in claim 1, wherein, a thickness of the oxidizedfilm is not less than 200 nm.
 5. The single-crystal silicon substrate asdefined in claim 2, wherein, a thickness of the oxidized film is notless than 200 nm.
 6. An SOI substrate in which a single-crystal thinfilm is provided on an insulating substrate, comprising: a bondedinterface at which an insulating film formed on the insulating substrateis bonded with a covering film with which the single-crystal siliconsubstrate is covered, the single-crystal silicon substrate beingseparated at a dense position of implanted hydrogen ions so that thesingle-crystal silicon thin film is formed, the insulating substratebeing a light-transmitting substrate, and the single-crystal siliconsubstrate being separated by means of heat treatment.
 7. An SOIsubstrate in which a single-crystal silicon thin film is provided on aninsulating substrate, comprising: a bonded interface at which aninsulating film formed on the insulating substrate is bonded with acovering film with which a single-crystal silicon substrate is covered,the single-crystal silicon thin film being formed by separating thesingle-crystal silicon substrate at a dense position of implantedhydrogen ions by means of heat treatment, and at the bonded interface,the insulating film is arranged to satisfy that a tan θ is not more than0.06, where θ is the angle between (i) a maximum slope curve ofmicro-roughness, the micro-roughness being measured in a 1-5 μm squareand not more than 5 nm in height, and (ii) an average surface plane. 8.An SOI substrate in which a single-crystal silicon thin film is providedon an insulating substrate, comprising: a bonded interface at which aninsulating film formed on the insulating substrate is bonded with acovering film with which a single-crystal silicon substrate is covered,the single-crystal silicon thin film being formed by separating thesingle-crystal silicon substrate at a dense position of implantedhydrogen ions by means of heat treatment, and contact angles of asurface of the insulating film and a surface of the covering film withrespect to water being not more than 10°.
 9. An SOI substrate in which asingle-crystal silicon thin film is provided on an insulating substrate,comprising: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate at a dense position of implanted hydrogen ions by means ofheat treatment, and the insulating film being an oxidized silicon filmformed by a plasma chemical vapor deposition method using a gas mixtureof a TEOS gas and an oxygen gas.
 10. An SOI substrate in which asingle-crystal silicon thin film is provided on an insulating substrate,comprising: a bonded interface at which an insulating film formed on theinsulating substrate is bonded with a covering film with which asingle-crystal silicon substrate is covered, the single-crystal siliconthin film being formed by separating the single-crystal siliconsubstrate at a dense position of implanted hydrogen ions by means ofheat treatment, and at the bonded interface, the insulating film whichis made of oxidized silicon and 5-300 nm thick being bonded.
 11. An SOIsubstrate in which a single-crystal silicon thin film is provided on aninsulating substrate, comprising: a bonded interface at which aninsulating film formed on the insulating substrate is bonded with acovering film with which a single-crystal silicon substrate is covered,the single-crystal silicon thin film being formed by separating thesingle-crystal silicon substrate at a dense position of implantedhydrogen ions by means of heat treatment, and a adhesive strength at thebonded interface being not less than 0.6 N/m.
 12. The SOI substrate asdefined in claim 6, wherein, a single-crystal thin-film device is formedon the single-crystal silicon substrate, and the single-crystalthin-film contains the single-crystal thin-film device being formed byseparating the single-crystal silicon substrate at the dense position bymeans of heat treatment.
 13. The SOI substrate as defined in claim 7,wherein, a single-crystal thin-film device is formed on thesingle-crystal silicon substrate, and the single-crystal thin-filmcontains the single-crystal thin-film device being formed by separatingthe single-crystal silicon substrate at the dense position by means ofheat treatment.
 14. The SOI substrate as defined in claim 6, furthercomprising: a single-crystal silicon thin-film device manufactured fromthe single-crystal silicon thin film; and a non-single-crystal siliconthin-film device which is manufactured from a non-single-crystal siliconthin film provided in an area on the insulating substrate, the areabeing different from an area where the single-crystal silicon thin filmis provided.
 15. The SOI substrate as defined in claim 7, furthercomprising: a single-crystal silicon thin-film device manufactured fromthe single-crystal silicon thin film; and a non-single-crystal siliconthin-film device which is manufactured from a non-single-crystal siliconthin film provided in an area on the insulating substrate, the areabeing different from an area where the single-crystal silicon thin filmis provided.
 16. A display device, comprising: an SOI substrateincluding a single-crystal silicon thin film provided on an insulatingsubstrate, on the single-crystal silicon thin film a semiconductordevice structure being formed, wherein, the SOI substrate includes abonded interface at which an insulating film formed on the insulatingsubstrate is bonded with a covering film with which a single-crystalsilicon substrate is covered, the single-crystal silicon substrate isseparated at a dense position of implanted hydrogen ions by heattreatment so that the single-crystal silicon thin film is formed, andthe insulating substrate is a light-transmitting substrate.
 17. Adisplay device, comprising: a semiconductor device in which anon-single-crystal silicon thin-film device and a single-crystal siliconthin-film device are provided on different areas of an insulatingsubstrate, the semiconductor device being used as an active matrixsubstrate of a display panel.
 18. A method of manufacturing asemiconductor device in which a single-crystal silicon thin-film devicemanufactured from a single-crystal silicon thin film and anon-single-crystal silicon thin film are formed on an insulatingsubstrate, wherein, after a circuit including the single-crystal siliconthin-film device is formed on the insulating substrate, thenon-single-crystal silicon thin film is formed.
 19. The method ofmanufacturing the semiconductor device as defined in claim 18, wherein,on the single-crystal silicon thin-film device, a protective interlayerinsulating film, a contact hole, and a metal wiring are formed.
 20. Themethod of manufacturing the semiconductor device as defined in claim 18,wherein, after the single-crystal silicon thin-film device is formed, aninterlayer insulating film is formed, and then the non-single-crystalsilicon thin film is formed.
 21. A method of manufacturing asemiconductor device in which a single-crystal silicon thin-film devicemanufactured from a single-crystal silicon thin film and anon-single-crystal silicon thin film are formed on an insulatingsubstrate, wherein, after the non-single-crystal silicon thin film isformed on the insulating substrate, the single-crystal silicon thin-filmdevice is formed.
 22. The method of manufacturing the semiconductordevice as defined in claim 18, wherein, the single-crystal siliconthin-film device is a MOS single-crystal silicon thin-film transistor.23. The method of manufacturing the semiconductor device as defined inclaim 21, wherein, the single-crystal silicon thin-film device is a MOSsingle-crystal silicon thin-film transistor.
 24. The method ofmanufacturing the semiconductor device as defined in claim 18, wherein,the single-crystal silicon thin-film device is a bipolar single-crystalsilicon thin-film transistor.
 25. The method of manufacturing thesemiconductor device as defined in claim 21, wherein, the single-crystalsilicon thin-film device is a bipolar single-crystal silicon thin-filmtransistor.
 26. The method of manufacturing the semiconductor device asdefined in claim 18, wherein, with respect to a single-crystal siliconsubstrate for manufacturing the single-crystal silicon thin-film device,a predetermined concentration of hydrogen ions is implanted for apredetermined depth.
 27. The method of manufacturing the semiconductordevice as defined in claim 21, wherein, with respect to a single-crystalsilicon substrate for manufacturing the single-crystal silicon thin-filmdevice, a predetermined concentration of hydrogen ions is implanted fora predetermined depth.
 28. The method of manufacturing the semiconductordevice as defined in claim 26, wherein, an energy for implanting thehydrogen ions is arranged so that an energy which is figured out bysubtracting an energy corresponding to a projection range of thehydrogen ions, the projection range corresponding to a thickness of anoxidized film, from the energy for implanting the hydrogen ions issmaller than an energy corresponding to a projection range of atomsconstituting a material in a layer formed on the oxidized film.
 29. Themethod of manufacturing the semiconductor device as defined in claim 27,wherein, an energy for implanting the hydrogen ions is arranged so thatan energy after subtracting an energy corresponding to a projectionrange of the hydrogen ions in a gate electrode material for a gateelectrode thickness from an incident energy of the hydrogen ions is nomore than an energy corresponding to a projection range of the heaviestions of gate constituent materials for a gate oxide thickness.
 30. Themethod of manufacturing the semiconductor device as defined in claim 26,wherein, a thickness of the single-crystal silicon substrate includingthe dense position is about not more than 100 μm.
 31. The method ofmanufacturing the semiconductor device as defined in claim 27, wherein,a thickness of the single-crystal silicon substrate including the denseposition is about not more than 100 μm.
 32. The method of manufacturingthe semiconductor device as defined in claim 21, wherein, after thenon-single-crystal silicon thin film is formed on the insulatingsubstrate, at least a surface area from which the non-single-crystalsilicon is removed and to which a single-crystal silicon is to be bondedis planarized in advance by performing a GCIB (Gas Cluster Ion Beam)using halide in approximately 3 keV.
 33. A method of manufacturing asemiconductor device, comprising the step of: (a) bonding an insulatingfilm formed on an insulating substrate with a covering film with which asingle-crystal silicon substrate is covered, the method furthercomprising the step of: (b) before the step (a), regulating a tangent ofa maximum slope of micro-roughness on a surface of the insulating filmto a surface plane of the insulating substrate, measured in a 1-5 μmsquare, is not more than 0.06, the micro-roughness being not more than 5nm in height.